Quote node names in aos_graph_nodes

Otherwise certain node names were failing to render with dot.

Change-Id: I2df3cf37dac20bdc3ed1f9f2e5ebb32aed38720c
diff --git a/aos/aos_graph_nodes.cc b/aos/aos_graph_nodes.cc
index 952c6b5..90778d1 100644
--- a/aos/aos_graph_nodes.cc
+++ b/aos/aos_graph_nodes.cc
@@ -84,8 +84,8 @@
         for (const aos::Connection *connection :
              *channel->destination_nodes()) {
           VLOG(1) << "Destination Node: " << connection->name()->string_view();
-          graph_out << "\t" << source_node_name << " -> "
-                    << connection->name()->c_str() << " [label=\""
+          graph_out << "\t\"" << source_node_name << "\" -> \""
+                    << connection->name()->c_str() << "\" [label=\""
                     << channel->name()->c_str() << "\\n"
                     << type_name << "\" color=\"" << color_map[source_node_name]
                     << "\"];" << std::endl;
@@ -95,8 +95,8 @@
   }
 
   // Write out all the nodes at the end, with their respective colors
-  for (const auto node_color : color_map) {
-    graph_out << "\t" << node_color.first << " [color=\"" << node_color.second
+  for (const auto &node_color : color_map) {
+    graph_out << "\t\"" << node_color.first << "\" [color=\"" << node_color.second
               << "\"];" << std::endl;
   }