Squashed 'third_party/allwpilib_2016/' content from commit 7f61816

Change-Id: If9d9245880859cdf580f5d7f77045135d0521ce7
git-subtree-dir: third_party/allwpilib_2016
git-subtree-split: 7f618166ed253a24629934fcf89c3decb0528a3b
diff --git a/wpilibc/shared/include/PIDSource.h b/wpilibc/shared/include/PIDSource.h
new file mode 100644
index 0000000..8f46ea4
--- /dev/null
+++ b/wpilibc/shared/include/PIDSource.h
@@ -0,0 +1,25 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2008. All Rights Reserved.
+ */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in $(WIND_BASE)/WPILib.  */
+/*----------------------------------------------------------------------------*/
+#pragma once
+
+enum class PIDSourceType { kDisplacement, kRate };
+
+/**
+ * PIDSource interface is a generic sensor source for the PID class.
+ * All sensors that can be used with the PID class will implement the PIDSource
+ * that
+ * returns a standard value that will be used in the PID code.
+ */
+class PIDSource {
+ public:
+  virtual void SetPIDSourceType(PIDSourceType pidSource);
+  PIDSourceType GetPIDSourceType() const;
+  virtual double PIDGet() = 0;
+
+ protected:
+  PIDSourceType m_pidSource = PIDSourceType::kDisplacement;
+};