diff --git a/js/message.js b/js/message.js
new file mode 100644
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+++ b/js/message.js
@@ -0,0 +1,1125 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/**
+ * @fileoverview Definition of jspb.Message.
+ *
+ * @author mwr@google.com (Mark Rawling)
+ */
+
+goog.provide('jspb.ExtensionFieldInfo');
+goog.provide('jspb.Message');
+
+goog.require('goog.array');
+goog.require('goog.asserts');
+goog.require('goog.json');
+goog.require('goog.object');
+
+// Not needed in compilation units that have no protos with xids.
+goog.forwardDeclare('xid.String');
+
+
+
+/**
+ * Stores information for a single extension field.
+ *
+ * For example, an extension field defined like so:
+ *
+ *     extend BaseMessage {
+ *       optional MyMessage my_field = 123;
+ *     }
+ *
+ * will result in an ExtensionFieldInfo object with these properties:
+ *
+ *     {
+ *       fieldIndex: 123,
+ *       fieldName: {my_field_renamed: 0},
+ *       ctor: proto.example.MyMessage,
+ *       toObjectFn: proto.example.MyMessage.toObject,
+ *       isRepeated: 0
+ *     }
+ *
+ * We include `toObjectFn` to allow the JSCompiler to perform dead-code removal
+ * on unused toObject() methods.
+ *
+ * If an extension field is primitive, ctor and toObjectFn will be null.
+ * isRepeated should be 0 or 1.
+ *
+ * binary{Reader,Writer}Fn and (if message type) binaryMessageSerializeFn are
+ * always provided. binaryReaderFn and binaryWriterFn are references to the
+ * appropriate methods on BinaryReader/BinaryWriter to read/write the value of
+ * this extension, and binaryMessageSerializeFn is a reference to the message
+ * class's .serializeBinary method, if available.
+ *
+ * @param {number} fieldNumber
+ * @param {Object} fieldName This has the extension field name as a property.
+ * @param {?function(new: jspb.Message, Array=)} ctor
+ * @param {?function((boolean|undefined),!jspb.Message):!Object} toObjectFn
+ * @param {number} isRepeated
+ * @param {?function(number,?)=} opt_binaryReaderFn
+ * @param {?function(number,?)|function(number,?,?,?,?,?)=} opt_binaryWriterFn
+ * @param {?function(?,?)=} opt_binaryMessageSerializeFn
+ * @param {?function(?,?)=} opt_binaryMessageDeserializeFn
+ * @param {?boolean=} opt_isPacked
+ * @constructor
+ * @struct
+ * @template T
+ */
+jspb.ExtensionFieldInfo = function(fieldNumber, fieldName, ctor, toObjectFn,
+    isRepeated, opt_binaryReaderFn, opt_binaryWriterFn,
+    opt_binaryMessageSerializeFn, opt_binaryMessageDeserializeFn,
+    opt_isPacked) {
+  /** @const */
+  this.fieldIndex = fieldNumber;
+  /** @const */
+  this.fieldName = fieldName;
+  /** @const */
+  this.ctor = ctor;
+  /** @const */
+  this.toObjectFn = toObjectFn;
+  /** @const */
+  this.binaryReaderFn = opt_binaryReaderFn;
+  /** @const */
+  this.binaryWriterFn = opt_binaryWriterFn;
+  /** @const */
+  this.binaryMessageSerializeFn = opt_binaryMessageSerializeFn;
+  /** @const */
+  this.binaryMessageDeserializeFn = opt_binaryMessageDeserializeFn;
+  /** @const */
+  this.isRepeated = isRepeated;
+  /** @const */
+  this.isPacked = opt_isPacked;
+};
+
+
+/**
+ * Base class for all JsPb messages.
+ * @constructor
+ * @struct
+ */
+jspb.Message = function() {
+};
+
+
+/**
+ * @define {boolean} Whether to generate toObject methods for objects. Turn
+ *     this off, if you do not want toObject to be ever used in your project.
+ *     When turning off this flag, consider adding a conformance test that bans
+ *     calling toObject. Enabling this will disable the JSCompiler's ability to
+ *     dead code eliminate fields used in protocol buffers that are never used
+ *     in an application.
+ */
+goog.define('jspb.Message.GENERATE_TO_OBJECT', true);
+
+
+/**
+ * @define {boolean} Whether to generate fromObject methods for objects. Turn
+ *     this off, if you do not want fromObject to be ever used in your project.
+ *     When turning off this flag, consider adding a conformance test that bans
+ *     calling fromObject. Enabling this might disable the JSCompiler's ability
+ *     to dead code eliminate fields used in protocol buffers that are never
+ *     used in an application.
+ *     NOTE: By default no protos actually have a fromObject method. You need to
+ *     add the jspb.generate_from_object options to the proto definition to
+ *     activate the feature.
+ *     By default this is enabled for test code only.
+ */
+goog.define('jspb.Message.GENERATE_FROM_OBJECT', !goog.DISALLOW_TEST_ONLY_CODE);
+
+
+/**
+ * @define {boolean} Turning on this flag does NOT change the behavior of JSPB
+ *     and only affects private internal state. It may, however, break some
+ *     tests that use naive deeply-equals algorithms, because using a proto
+ *     mutates its internal state.
+ *     Projects are advised to turn this flag always on.
+ */
+goog.define('jspb.Message.MINIMIZE_MEMORY_ALLOCATIONS', COMPILED);
+// TODO(b/19419436) Turn this on by default.
+
+
+/**
+ * The internal data array.
+ * @type {!Array}
+ * @protected
+ */
+jspb.Message.prototype.array;
+
+
+/**
+ * Wrappers are the constructed instances of message-type fields. They are built
+ * on demand from the raw array data. Includes message fields, repeated message
+ * fields and extension message fields. Indexed by field number.
+ * @type {Object}
+ * @private
+ */
+jspb.Message.prototype.wrappers_;
+
+
+/**
+ * The object that contains extension fields, if any. This is an object that
+ * maps from a proto field number to the field's value.
+ * @type {Object}
+ * @private
+ */
+jspb.Message.prototype.extensionObject_;
+
+
+/**
+ * Non-extension fields with a field number at or above the pivot are
+ * stored in the extension object (in addition to all extension fields).
+ * @type {number}
+ * @private
+ */
+jspb.Message.prototype.pivot_;
+
+
+/**
+ * The JsPb message_id of this proto.
+ * @type {string|undefined} the message id or undefined if this message
+ *     has no id.
+ * @private
+ */
+jspb.Message.prototype.messageId_;
+
+
+/**
+ * The xid of this proto type (The same for all instances of a proto). Provides
+ * a way to identify a proto by stable obfuscated name.
+ * @see {xid}.
+ * Available if {@link jspb.generate_xid} is added as a Message option to
+ * a protocol buffer.
+ * @const {!xid.String|undefined} The xid or undefined if message is
+ *     annotated to generate the xid.
+ */
+jspb.Message.prototype.messageXid;
+
+
+
+/**
+ * Returns the JsPb message_id of this proto.
+ * @return {string|undefined} the message id or undefined if this message
+ *     has no id.
+ */
+jspb.Message.prototype.getJsPbMessageId = function() {
+  return this.messageId_;
+};
+
+
+/**
+ * An offset applied to lookups into this.array to account for the presence or
+ * absence of a messageId at position 0. For response messages, this will be 0.
+ * Otherwise, it will be -1 so that the first array position is not wasted.
+ * @type {number}
+ * @private
+ */
+jspb.Message.prototype.arrayIndexOffset_;
+
+
+/**
+ * Returns the index into msg.array at which the proto field with tag number
+ * fieldNumber will be located.
+ * @param {!jspb.Message} msg Message for which we're calculating an index.
+ * @param {number} fieldNumber The field number.
+ * @return {number} The index.
+ * @private
+ */
+jspb.Message.getIndex_ = function(msg, fieldNumber) {
+  return fieldNumber + msg.arrayIndexOffset_;
+};
+
+
+/**
+ * Initializes a JsPb Message.
+ * @param {!jspb.Message} msg The JsPb proto to modify.
+ * @param {Array|undefined} data An initial data array.
+ * @param {string|number} messageId For response messages, the message id or ''
+ *     if no message id is specified. For non-response messages, 0.
+ * @param {number} suggestedPivot The field number at which to start putting
+ *     fields into the extension object. This is only used if data does not
+ *     contain an extension object already. -1 if no extension object is
+ *     required for this message type.
+ * @param {Array<number>} repeatedFields The message's repeated fields.
+ * @param {Array<!Array<number>>=} opt_oneofFields The fields belonging to
+ *     each of the message's oneof unions.
+ * @protected
+ */
+jspb.Message.initialize = function(
+    msg, data, messageId, suggestedPivot, repeatedFields, opt_oneofFields) {
+  msg.wrappers_ = jspb.Message.MINIMIZE_MEMORY_ALLOCATIONS ? null : {};
+  if (!data) {
+    data = messageId ? [messageId] : [];
+  }
+  msg.messageId_ = messageId ? String(messageId) : undefined;
+  // If the messageId is 0, this message is not a response message, so we shift
+  // array indices down by 1 so as not to waste the first position in the array,
+  // which would otherwise go unused.
+  msg.arrayIndexOffset_ = messageId === 0 ? -1 : 0;
+  msg.array = data;
+  jspb.Message.materializeExtensionObject_(msg, suggestedPivot);
+  if (repeatedFields) {
+    for (var i = 0; i < repeatedFields.length; i++) {
+      var fieldNumber = repeatedFields[i];
+      if (fieldNumber < msg.pivot_) {
+        var index = jspb.Message.getIndex_(msg, fieldNumber);
+        msg.array[index] = msg.array[index] ||
+            (jspb.Message.MINIMIZE_MEMORY_ALLOCATIONS ?
+                jspb.Message.EMPTY_LIST_SENTINEL_ :
+                []);
+      } else {
+        msg.extensionObject_[fieldNumber] =
+            msg.extensionObject_[fieldNumber] ||
+            (jspb.Message.MINIMIZE_MEMORY_ALLOCATIONS ?
+                jspb.Message.EMPTY_LIST_SENTINEL_ :
+                []);
+      }
+    }
+  }
+
+  if (opt_oneofFields && opt_oneofFields.length) {
+    // Compute the oneof case for each union. This ensures only one value is
+    // set in the union.
+    goog.array.forEach(
+        opt_oneofFields, goog.partial(jspb.Message.computeOneofCase, msg));
+  }
+};
+
+
+/**
+ * Used to mark empty repeated fields. Serializes to null when serialized
+ * to JSON.
+ * When reading a repeated field readers must check the return value against
+ * this value and return and replace it with a new empty array if it is
+ * present.
+ * @private @const {!Object}
+ */
+jspb.Message.EMPTY_LIST_SENTINEL_ = goog.DEBUG && Object.freeze ?
+    Object.freeze([]) :
+    [];
+
+
+/**
+ * Ensures that the array contains an extension object if necessary.
+ * If the array contains an extension object in its last position, then the
+ * object is kept in place and its position is used as the pivot.  If not, then
+ * create an extension object using suggestedPivot.  If suggestedPivot is -1,
+ * we don't have an extension object at all, in which case all fields are stored
+ * in the array.
+ * @param {!jspb.Message} msg The JsPb proto to modify.
+ * @param {number} suggestedPivot See description for initialize().
+ * @private
+ */
+jspb.Message.materializeExtensionObject_ = function(msg, suggestedPivot) {
+  if (msg.array.length) {
+    var foundIndex = msg.array.length - 1;
+    var obj = msg.array[foundIndex];
+    // Normal fields are never objects, so we can be sure that if we find an
+    // object here, then it's the extension object. However, we must ensure that
+    // the object is not an array, since arrays are valid field values.
+    // NOTE(lukestebbing): We avoid looking at .length to avoid a JIT bug
+    // in Safari on iOS 8. See the description of CL/86511464 for details.
+    if (obj && typeof obj == 'object' && !goog.isArray(obj)) {
+      msg.pivot_ = foundIndex - msg.arrayIndexOffset_;
+      msg.extensionObject_ = obj;
+      return;
+    }
+  }
+  // This complexity exists because we keep all extension fields in the
+  // extensionObject_ regardless of proto field number. Changing this would
+  // simplify the code here, but it would require changing the serialization
+  // format from the server, which is not backwards compatible.
+  // TODO(jshneier): Should we just treat extension fields the same as
+  // non-extension fields, and select whether they appear in the object or in
+  // the array purely based on tag number? This would allow simplifying all the
+  // get/setExtension logic, but it would require the breaking change described
+  // above.
+  if (suggestedPivot > -1) {
+    msg.pivot_ = suggestedPivot;
+    var pivotIndex = jspb.Message.getIndex_(msg, suggestedPivot);
+    if (!jspb.Message.MINIMIZE_MEMORY_ALLOCATIONS) {
+      msg.extensionObject_ = msg.array[pivotIndex] = {};
+    } else {
+      // Initialize to null to avoid changing the shape of the proto when it
+      // gets eventually set.
+      msg.extensionObject_ = null;
+    }
+  } else {
+    msg.pivot_ = Number.MAX_VALUE;
+  }
+};
+
+
+/**
+ * Creates an empty extensionObject_ if non exists.
+ * @param {!jspb.Message} msg The JsPb proto to modify.
+ * @private
+ */
+jspb.Message.maybeInitEmptyExtensionObject_ = function(msg) {
+  var pivotIndex = jspb.Message.getIndex_(msg, msg.pivot_);
+  if (!msg.array[pivotIndex]) {
+    msg.extensionObject_ = msg.array[pivotIndex] = {};
+  }
+};
+
+
+/**
+ * Converts a JsPb repeated message field into an object list.
+ * @param {!Array<T>} field The repeated message field to be
+ *     converted.
+ * @param {?function(boolean=): Object|
+ *     function((boolean|undefined),T): Object} toObjectFn The toObject
+ *     function for this field.  We need to pass this for effective dead code
+ *     removal.
+ * @param {boolean=} opt_includeInstance Whether to include the JSPB instance
+ *     for transitional soy proto support: http://goto/soy-param-migration
+ * @return {!Array<Object>} An array of converted message objects.
+ * @template T
+ */
+jspb.Message.toObjectList = function(field, toObjectFn, opt_includeInstance) {
+  // Not using goog.array.map in the generated code to keep it small.
+  // And not using it here to avoid a function call.
+  var result = [];
+  for (var i = 0; i < field.length; i++) {
+    result[i] = toObjectFn.call(field[i], opt_includeInstance,
+      /** @type {!jspb.Message} */ (field[i]));
+  }
+  return result;
+};
+
+
+/**
+ * Adds a proto's extension data to a Soy rendering object.
+ * @param {!jspb.Message} proto The proto whose extensions to convert.
+ * @param {!Object} obj The Soy object to add converted extension data to.
+ * @param {!Object} extensions The proto class' registered extensions.
+ * @param {function(jspb.ExtensionFieldInfo) : *} getExtensionFn The proto
+ *     class' getExtension function. Passed for effective dead code removal.
+ * @param {boolean=} opt_includeInstance Whether to include the JSPB instance
+ *     for transitional soy proto support: http://goto/soy-param-migration
+ */
+jspb.Message.toObjectExtension = function(proto, obj, extensions,
+    getExtensionFn, opt_includeInstance) {
+  for (var fieldNumber in extensions) {
+    var fieldInfo = extensions[fieldNumber];
+    var value = getExtensionFn.call(proto, fieldInfo);
+    if (value) {
+      for (var name in fieldInfo.fieldName) {
+        if (fieldInfo.fieldName.hasOwnProperty(name)) {
+          break; // the compiled field name
+        }
+      }
+      if (!fieldInfo.toObjectFn) {
+        obj[name] = value;
+      } else {
+        if (fieldInfo.isRepeated) {
+          obj[name] = jspb.Message.toObjectList(
+              /** @type {!Array<jspb.Message>} */ (value),
+              fieldInfo.toObjectFn, opt_includeInstance);
+        } else {
+          obj[name] = fieldInfo.toObjectFn(opt_includeInstance, value);
+        }
+      }
+    }
+  }
+};
+
+
+/**
+ * Writes a proto's extension data to a binary-format output stream.
+ * @param {!jspb.Message} proto The proto whose extensions to convert.
+ * @param {*} writer The binary-format writer to write to.
+ * @param {!Object} extensions The proto class' registered extensions.
+ * @param {function(jspb.ExtensionFieldInfo) : *} getExtensionFn The proto
+ *     class' getExtension function. Passed for effective dead code removal.
+ */
+jspb.Message.serializeBinaryExtensions = function(proto, writer, extensions,
+    getExtensionFn) {
+  for (var fieldNumber in extensions) {
+    var fieldInfo = extensions[fieldNumber];
+    // The old codegen doesn't add the extra fields to ExtensionFieldInfo, so we
+    // need to gracefully error-out here rather than produce a null dereference
+    // below.
+    if (!fieldInfo.binaryWriterFn) {
+      throw new Error('Message extension present that was generated ' +
+                      'without binary serialization support');
+    }
+    var value = getExtensionFn.call(proto, fieldInfo);
+    if (value) {
+      if (fieldInfo.ctor) {  // is this a message type?
+        // If the message type of the extension was generated without binary
+        // support, there may not be a binary message serializer function, and
+        // we can't know when we codegen the extending message that the extended
+        // message may require binary support, so we can *only* catch this error
+        // here, at runtime (and this decoupled codegen is the whole point of
+        // extensions!).
+        if (fieldInfo.binaryMessageSerializeFn) {
+          fieldInfo.binaryWriterFn.call(writer, fieldInfo.fieldIndex,
+              value, fieldInfo.binaryMessageSerializeFn);
+        } else {
+          throw new Error('Message extension present holding submessage ' +
+                          'without binary support enabled, and message is ' +
+                          'being serialized to binary format');
+        }
+      } else {
+        fieldInfo.binaryWriterFn.call(writer, fieldInfo.fieldIndex, value);
+      }
+    }
+  }
+};
+
+
+/**
+ * Reads an extension field from the given reader and, if a valid extension,
+ * sets the extension value.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {{skipField:function(),getFieldNumber:function():number}} reader
+ * @param {!Object} extensions The extensions object.
+ * @param {function(jspb.ExtensionFieldInfo)} getExtensionFn
+ * @param {function(jspb.ExtensionFieldInfo, ?)} setExtensionFn
+ */
+jspb.Message.readBinaryExtension = function(msg, reader, extensions,
+    getExtensionFn, setExtensionFn) {
+  var fieldInfo = extensions[reader.getFieldNumber()];
+  if (!fieldInfo) {
+    reader.skipField();
+    return;
+  }
+  if (!fieldInfo.binaryReaderFn) {
+    throw new Error('Deserializing extension whose generated code does not ' +
+                    'support binary format');
+  }
+
+  var value;
+  if (fieldInfo.ctor) {
+    // Message type.
+    value = new fieldInfo.ctor();
+    fieldInfo.binaryReaderFn.call(
+        reader, value, fieldInfo.binaryMessageDeserializeFn);
+  } else {
+    // All other types.
+    value = fieldInfo.binaryReaderFn.call(reader);
+  }
+
+  if (fieldInfo.isRepeated && !fieldInfo.isPacked) {
+    var currentList = getExtensionFn.call(msg, fieldInfo);
+    if (!currentList) {
+      setExtensionFn.call(msg, fieldInfo, [value]);
+    } else {
+      currentList.push(value);
+    }
+  } else {
+    setExtensionFn.call(msg, fieldInfo, value);
+  }
+};
+
+
+/**
+ * Gets the value of a non-extension field.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @return {string|number|boolean|Uint8Array|Array|null|undefined}
+ * The field's value.
+ * @protected
+ */
+jspb.Message.getField = function(msg, fieldNumber) {
+  if (fieldNumber < msg.pivot_) {
+    var index = jspb.Message.getIndex_(msg, fieldNumber);
+    var val = msg.array[index];
+    if (val === jspb.Message.EMPTY_LIST_SENTINEL_) {
+      return msg.array[index] = [];
+    }
+    return val;
+  } else {
+    var val = msg.extensionObject_[fieldNumber];
+    if (val === jspb.Message.EMPTY_LIST_SENTINEL_) {
+      return msg.extensionObject_[fieldNumber] = [];
+    }
+    return val;
+  }
+};
+
+
+/**
+ * Gets the value of a non-extension primitive field, with proto3 (non-nullable
+ * primitives) semantics. Returns `defaultValue` if the field is not otherwise
+ * set.
+ * @template T
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {T} defaultValue The default value.
+ * @return {T} The field's value.
+ * @protected
+ */
+jspb.Message.getFieldProto3 = function(msg, fieldNumber, defaultValue) {
+  var value = jspb.Message.getField(msg, fieldNumber);
+  if (value == null) {
+    return defaultValue;
+  } else {
+    return value;
+  }
+};
+
+
+/**
+ * Sets the value of a non-extension field.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {string|number|boolean|Uint8Array|Array|undefined} value New value
+ * @protected
+ */
+jspb.Message.setField = function(msg, fieldNumber, value) {
+  if (fieldNumber < msg.pivot_) {
+    msg.array[jspb.Message.getIndex_(msg, fieldNumber)] = value;
+  } else {
+    msg.extensionObject_[fieldNumber] = value;
+  }
+};
+
+
+/**
+ * Sets the value of a field in a oneof union and clears all other fields in
+ * the union.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {!Array<number>} oneof The fields belonging to the union.
+ * @param {string|number|boolean|Uint8Array|Array|undefined} value New value
+ * @protected
+ */
+jspb.Message.setOneofField = function(msg, fieldNumber, oneof, value) {
+  var currentCase = jspb.Message.computeOneofCase(msg, oneof);
+  if (currentCase && currentCase !== fieldNumber && value !== undefined) {
+    if (msg.wrappers_ && currentCase in msg.wrappers_) {
+      msg.wrappers_[currentCase] = undefined;
+    }
+    jspb.Message.setField(msg, currentCase, undefined);
+  }
+  jspb.Message.setField(msg, fieldNumber, value);
+};
+
+
+/**
+ * Computes the selection in a oneof group for the given message, ensuring
+ * only one field is set in the process.
+ *
+ * According to the protobuf language guide (
+ * https://developers.google.com/protocol-buffers/docs/proto#oneof), "if the
+ * parser encounters multiple members of the same oneof on the wire, only the
+ * last member seen is used in the parsed message." Since JSPB serializes
+ * messages to a JSON array, the "last member seen" will always be the field
+ * with the greatest field number (directly corresponding to the greatest
+ * array index).
+ *
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {!Array<number>} oneof The field numbers belonging to the union.
+ * @return {number} The field number currently set in the union, or 0 if none.
+ * @protected
+ */
+jspb.Message.computeOneofCase = function(msg, oneof) {
+  var oneofField;
+  var oneofValue;
+
+  goog.array.forEach(oneof, function(fieldNumber) {
+    var value = jspb.Message.getField(msg, fieldNumber);
+    if (goog.isDefAndNotNull(value)) {
+      oneofField = fieldNumber;
+      oneofValue = value;
+      jspb.Message.setField(msg, fieldNumber, undefined);
+    }
+  });
+
+  if (oneofField) {
+    // NB: We know the value is unique, so we can call jspb.Message.setField
+    // directly instead of jpsb.Message.setOneofField. Also, setOneofField
+    // calls this function.
+    jspb.Message.setField(msg, oneofField, oneofValue);
+    return oneofField;
+  }
+
+  return 0;
+};
+
+
+/**
+ * Gets and wraps a proto field on access.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {function(new:jspb.Message, Array)} ctor Constructor for the field.
+ * @param {number} fieldNumber The field number.
+ * @param {number=} opt_required True (1) if this is a required field.
+ * @return {jspb.Message} The field as a jspb proto.
+ * @protected
+ */
+jspb.Message.getWrapperField = function(msg, ctor, fieldNumber, opt_required) {
+  // TODO(mwr): Consider copying data and/or arrays.
+  if (!msg.wrappers_) {
+    msg.wrappers_ = {};
+  }
+  if (!msg.wrappers_[fieldNumber]) {
+    var data = /** @type {Array} */ (jspb.Message.getField(msg, fieldNumber));
+    if (opt_required || data) {
+      // TODO(mwr): Remove existence test for always valid default protos.
+      msg.wrappers_[fieldNumber] = new ctor(data);
+    }
+  }
+  return /** @type {jspb.Message} */ (msg.wrappers_[fieldNumber]);
+};
+
+
+/**
+ * Gets and wraps a repeated proto field on access.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {function(new:jspb.Message, Array)} ctor Constructor for the field.
+ * @param {number} fieldNumber The field number.
+ * @return {Array<!jspb.Message>} The repeated field as an array of protos.
+ * @protected
+ */
+jspb.Message.getRepeatedWrapperField = function(msg, ctor, fieldNumber) {
+  if (!msg.wrappers_) {
+    msg.wrappers_ = {};
+  }
+  if (!msg.wrappers_[fieldNumber]) {
+    var data = jspb.Message.getField(msg, fieldNumber);
+    for (var wrappers = [], i = 0; i < data.length; i++) {
+      wrappers[i] = new ctor(data[i]);
+    }
+    msg.wrappers_[fieldNumber] = wrappers;
+  }
+  var val = msg.wrappers_[fieldNumber];
+  if (val == jspb.Message.EMPTY_LIST_SENTINEL_) {
+    val = msg.wrappers_[fieldNumber] = [];
+  }
+  return /** @type {Array<!jspb.Message>} */ (val);
+};
+
+
+/**
+ * Sets a proto field and syncs it to the backing array.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {jspb.Message|undefined} value A new value for this proto field.
+ * @protected
+ */
+jspb.Message.setWrapperField = function(msg, fieldNumber, value) {
+  if (!msg.wrappers_) {
+    msg.wrappers_ = {};
+  }
+  var data = value ? value.toArray() : value;
+  msg.wrappers_[fieldNumber] = value;
+  jspb.Message.setField(msg, fieldNumber, data);
+};
+
+
+/**
+ * Sets a proto field in a oneof union and syncs it to the backing array.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {!Array<number>} oneof The fields belonging to the union.
+ * @param {jspb.Message|undefined} value A new value for this proto field.
+ * @protected
+ */
+jspb.Message.setOneofWrapperField = function(msg, fieldNumber, oneof, value) {
+  if (!msg.wrappers_) {
+    msg.wrappers_ = {};
+  }
+  var data = value ? value.toArray() : value;
+  msg.wrappers_[fieldNumber] = value;
+  jspb.Message.setOneofField(msg, fieldNumber, oneof, data);
+};
+
+
+/**
+ * Sets a repeated proto field and syncs it to the backing array.
+ * @param {!jspb.Message} msg A jspb proto.
+ * @param {number} fieldNumber The field number.
+ * @param {Array<!jspb.Message>|undefined} value An array of protos.
+ * @protected
+ */
+jspb.Message.setRepeatedWrapperField = function(msg, fieldNumber, value) {
+  if (!msg.wrappers_) {
+    msg.wrappers_ = {};
+  }
+  value = value || [];
+  for (var data = [], i = 0; i < value.length; i++) {
+    data[i] = value[i].toArray();
+  }
+  msg.wrappers_[fieldNumber] = value;
+  jspb.Message.setField(msg, fieldNumber, data);
+};
+
+
+/**
+ * Converts a JsPb repeated message field into a map. The map will contain
+ * protos unless an optional toObject function is given, in which case it will
+ * contain objects suitable for Soy rendering.
+ * @param {!Array<T>} field The repeated message field to be
+ *     converted.
+ * @param {function() : string?} mapKeyGetterFn The function to get the key of
+ *     the map.
+ * @param {?function(boolean=): Object|
+ *     function((boolean|undefined),T): Object} opt_toObjectFn The
+ *     toObject function for this field. We need to pass this for effective
+ *     dead code removal.
+ * @param {boolean=} opt_includeInstance Whether to include the JSPB instance
+ *     for transitional soy proto support: http://goto/soy-param-migration
+ * @return {!Object.<string, Object>} A map of proto or Soy objects.
+ * @template T
+ */
+jspb.Message.toMap = function(
+    field, mapKeyGetterFn, opt_toObjectFn, opt_includeInstance) {
+  var result = {};
+  for (var i = 0; i < field.length; i++) {
+    result[mapKeyGetterFn.call(field[i])] = opt_toObjectFn ?
+        opt_toObjectFn.call(field[i], opt_includeInstance,
+            /** @type {!jspb.Message} */ (field[i])) : field[i];
+  }
+  return result;
+};
+
+
+/**
+ * Returns the internal array of this proto.
+ * <p>Note: If you use this array to construct a second proto, the content
+ * would then be partially shared between the two protos.
+ * @return {!Array} The proto represented as an array.
+ */
+jspb.Message.prototype.toArray = function() {
+  return this.array;
+};
+
+
+
+
+/**
+ * Creates a string representation of the internal data array of this proto.
+ * <p>NOTE: This string is *not* suitable for use in server requests.
+ * @return {string} A string representation of this proto.
+ * @override
+ */
+jspb.Message.prototype.toString = function() {
+  return this.array.toString();
+};
+
+
+/**
+ * Gets the value of the extension field from the extended object.
+ * @param {jspb.ExtensionFieldInfo.<T>} fieldInfo Specifies the field to get.
+ * @return {T} The value of the field.
+ * @template T
+ */
+jspb.Message.prototype.getExtension = function(fieldInfo) {
+  if (!this.extensionObject_) {
+    return undefined;
+  }
+  if (!this.wrappers_) {
+    this.wrappers_ = {};
+  }
+  var fieldNumber = fieldInfo.fieldIndex;
+  if (fieldInfo.isRepeated) {
+    if (fieldInfo.ctor) {
+      if (!this.wrappers_[fieldNumber]) {
+        this.wrappers_[fieldNumber] =
+            goog.array.map(this.extensionObject_[fieldNumber] || [],
+                function(arr) {
+                  return new fieldInfo.ctor(arr);
+                });
+      }
+      return this.wrappers_[fieldNumber];
+    } else {
+      return this.extensionObject_[fieldNumber];
+    }
+  } else {
+    if (fieldInfo.ctor) {
+      if (!this.wrappers_[fieldNumber] && this.extensionObject_[fieldNumber]) {
+        this.wrappers_[fieldNumber] = new fieldInfo.ctor(
+            /** @type {Array|undefined} */ (
+                this.extensionObject_[fieldNumber]));
+      }
+      return this.wrappers_[fieldNumber];
+    } else {
+      return this.extensionObject_[fieldNumber];
+    }
+  }
+};
+
+
+/**
+ * Sets the value of the extension field in the extended object.
+ * @param {jspb.ExtensionFieldInfo} fieldInfo Specifies the field to set.
+ * @param {jspb.Message|string|number|boolean|Array} value The value to set.
+ */
+jspb.Message.prototype.setExtension = function(fieldInfo, value) {
+  if (!this.wrappers_) {
+    this.wrappers_ = {};
+  }
+  jspb.Message.maybeInitEmptyExtensionObject_(this);
+  var fieldNumber = fieldInfo.fieldIndex;
+  if (fieldInfo.isRepeated) {
+    value = value || [];
+    if (fieldInfo.ctor) {
+      this.wrappers_[fieldNumber] = value;
+      this.extensionObject_[fieldNumber] = goog.array.map(
+          /** @type {Array<jspb.Message>} */ (value), function(msg) {
+        return msg.toArray();
+      });
+    } else {
+      this.extensionObject_[fieldNumber] = value;
+    }
+  } else {
+    if (fieldInfo.ctor) {
+      this.wrappers_[fieldNumber] = value;
+      this.extensionObject_[fieldNumber] = value ? value.toArray() : value;
+    } else {
+      this.extensionObject_[fieldNumber] = value;
+    }
+  }
+};
+
+
+/**
+ * Creates a difference object between two messages.
+ *
+ * The result will contain the top-level fields of m2 that differ from those of
+ * m1 at any level of nesting. No data is cloned, the result object will
+ * share its top-level elements with m2 (but not with m1).
+ *
+ * Note that repeated fields should not have null/undefined elements, but if
+ * they do, this operation will treat repeated fields of different length as
+ * the same if the only difference between them is due to trailing
+ * null/undefined values.
+ *
+ * @param {!jspb.Message} m1 The first message object.
+ * @param {!jspb.Message} m2 The second message object.
+ * @return {!jspb.Message} The difference returned as a proto message.
+ *     Note that the returned message may be missing required fields. This is
+ *     currently tolerated in Js, but would cause an error if you tried to
+ *     send such a proto to the server. You can access the raw difference
+ *     array with result.toArray().
+ * @throws {Error} If the messages are responses with different types.
+ */
+jspb.Message.difference = function(m1, m2) {
+  if (!(m1 instanceof m2.constructor)) {
+    throw new Error('Messages have different types.');
+  }
+  var arr1 = m1.toArray();
+  var arr2 = m2.toArray();
+  var res = [];
+  var start = 0;
+  var length = arr1.length > arr2.length ? arr1.length : arr2.length;
+  if (m1.getJsPbMessageId()) {
+    res[0] = m1.getJsPbMessageId();
+    start = 1;
+  }
+  for (var i = start; i < length; i++) {
+    if (!jspb.Message.compareFields(arr1[i], arr2[i])) {
+      res[i] = arr2[i];
+    }
+  }
+  return new m1.constructor(res);
+};
+
+
+/**
+ * Tests whether two messages are equal.
+ * @param {jspb.Message|undefined} m1 The first message object.
+ * @param {jspb.Message|undefined} m2 The second message object.
+ * @return {boolean} true if both messages are null/undefined, or if both are
+ *     of the same type and have the same field values.
+ */
+jspb.Message.equals = function(m1, m2) {
+  return m1 == m2 || (!!(m1 && m2) && (m1 instanceof m2.constructor) &&
+      jspb.Message.compareFields(m1.toArray(), m2.toArray()));
+};
+
+
+/**
+ * Compares two message fields recursively.
+ * @param {*} field1 The first field.
+ * @param {*} field2 The second field.
+ * @return {boolean} true if the fields are null/undefined, or otherwise equal.
+ */
+jspb.Message.compareFields = function(field1, field2) {
+  if (goog.isObject(field1) && goog.isObject(field2)) {
+    var keys = {}, name, extensionObject1, extensionObject2;
+    for (name in field1) {
+      field1.hasOwnProperty(name) && (keys[name] = 0);
+    }
+    for (name in field2) {
+      field2.hasOwnProperty(name) && (keys[name] = 0);
+    }
+    for (name in keys) {
+      var val1 = field1[name], val2 = field2[name];
+      if (goog.isObject(val1) && !goog.isArray(val1)) {
+        if (extensionObject1 !== undefined) {
+          throw new Error('invalid jspb state');
+        }
+        extensionObject1 = goog.object.isEmpty(val1) ? undefined : val1;
+        val1 = undefined;
+      }
+      if (goog.isObject(val2) && !goog.isArray(val2)) {
+        if (extensionObject2 !== undefined) {
+          throw new Error('invalid jspb state');
+        }
+        extensionObject2 = goog.object.isEmpty(val2) ? undefined : val2;
+        val2 = undefined;
+      }
+      if (!jspb.Message.compareFields(val1, val2)) {
+        return false;
+      }
+    }
+    if (extensionObject1 || extensionObject2) {
+      return jspb.Message.compareFields(extensionObject1, extensionObject2);
+    }
+    return true;
+  }
+  // Primitive fields, null and undefined compare as equal.
+  // This also forces booleans and 0/1 to compare as equal to ensure
+  // compatibility with the jspb serializer.
+  return field1 == field2;
+};
+
+
+/**
+ * Static clone function. NOTE: A type-safe method called "cloneMessage" exists
+ * on each generated JsPb class. Do not call this function directly.
+ * @param {!jspb.Message} msg A message to clone.
+ * @return {!jspb.Message} A deep clone of the given message.
+ */
+jspb.Message.clone = function(msg) {
+  // Although we could include the wrappers, we leave them out here.
+  return jspb.Message.cloneMessage(msg);
+};
+
+
+/**
+ * @param {!jspb.Message} msg A message to clone.
+ * @return {!jspb.Message} A deep clone of the given message.
+ * @protected
+ */
+jspb.Message.cloneMessage = function(msg) {
+  // Although we could include the wrappers, we leave them out here.
+  return new msg.constructor(jspb.Message.clone_(msg.toArray()));
+};
+
+
+/**
+ * Takes 2 messages of the same type and copies the contents of the first
+ * message into the second. After this the 2 messages will equals in terms of
+ * value semantics but share no state. All data in the destination message will
+ * be overridden.
+ *
+ * @param {MESSAGE} fromMessage Message that will be copied into toMessage.
+ * @param {MESSAGE} toMessage Message which will receive a copy of fromMessage
+ *     as its contents.
+ * @template MESSAGE
+ */
+jspb.Message.copyInto = function(fromMessage, toMessage) {
+  goog.asserts.assertInstanceof(fromMessage, jspb.Message);
+  goog.asserts.assertInstanceof(toMessage, jspb.Message);
+  goog.asserts.assert(fromMessage.constructor == toMessage.constructor,
+      'Copy source and target message should have the same type.');
+  var copyOfFrom = jspb.Message.clone(fromMessage);
+
+  var to = toMessage.toArray();
+  var from = copyOfFrom.toArray();
+
+  // Empty destination in case it has more values at the end of the array.
+  to.length = 0;
+  // and then copy everything from the new to the existing message.
+  for (var i = 0; i < from.length; i++) {
+    to[i] = from[i];
+  }
+
+  // This is either null or empty for a fresh copy.
+  toMessage.wrappers_ = copyOfFrom.wrappers_;
+  // Just a reference into the shared array.
+  toMessage.extensionObject_ = copyOfFrom.extensionObject_;
+};
+
+
+/**
+ * Helper for cloning an internal JsPb object.
+ * @param {!Object} obj A JsPb object, eg, a field, to be cloned.
+ * @return {!Object} A clone of the input object.
+ * @private
+ */
+jspb.Message.clone_ = function(obj) {
+  var o;
+  if (goog.isArray(obj)) {
+    // Allocate array of correct size.
+    var clonedArray = new Array(obj.length);
+    // Use array iteration where possible because it is faster than for-in.
+    for (var i = 0; i < obj.length; i++) {
+      if ((o = obj[i]) != null) {
+        clonedArray[i] = typeof o == 'object' ? jspb.Message.clone_(o) : o;
+      }
+    }
+    return clonedArray;
+  }
+  var clone = {};
+  for (var key in obj) {
+    if ((o = obj[key]) != null) {
+      clone[key] = typeof o == 'object' ? jspb.Message.clone_(o) : o;
+    }
+  }
+  return clone;
+};
+
+
+/**
+ * Registers a JsPb message type id with its constructor.
+ * @param {string} id The id for this type of message.
+ * @param {Function} constructor The message constructor.
+ */
+jspb.Message.registerMessageType = function(id, constructor) {
+  jspb.Message.registry_[id] = constructor;
+  // This is needed so we can later access messageId directly on the contructor,
+  // otherwise it is not available due to 'property collapsing' by the compiler.
+  constructor.messageId = id;
+};
+
+
+/**
+ * The registry of message ids to message constructors.
+ * @private
+ */
+jspb.Message.registry_ = {};
+
+
+/**
+ * The extensions registered on MessageSet. This is a map of extension
+ * field number to field info object. This should be considered as a
+ * private API.
+ *
+ * This is similar to [jspb class name].extensions object for
+ * non-MessageSet. We special case MessageSet so that we do not need
+ * to goog.require MessageSet from classes that extends MessageSet.
+ *
+ * @type {!Object.<number, jspb.ExtensionFieldInfo>}
+ */
+jspb.Message.messageSetExtensions = {};