Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/reflection_ops.cc

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// 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
@@ skipping 35 matching lines @@
   if (&from == to) return;
   Clear(to);
   Merge(from, to);
 }
 
 void ReflectionOps::Merge(const Message& from, Message* to) {
   GOOGLE_CHECK_NE(&from, to);
 
   const Descriptor* descriptor = from.GetDescriptor();
   GOOGLE_CHECK_EQ(to->GetDescriptor(), descriptor)
-    << "Tried to merge messages of different types.";
+    << "Tried to merge messages of different types "
+    << "(merge " << descriptor->full_name()
+    << " to " << to->GetDescriptor()->full_name() << ")";
 
   const Reflection* from_reflection = from.GetReflection();
   const Reflection* to_reflection = to->GetReflection();
 
   vector<const FieldDescriptor*> fields;
   from_reflection->ListFields(from, &fields);
   for (int i = 0; i < fields.size(); i++) {
     const FieldDescriptor* field = fields[i];
 
     if (field->is_repeated()) {
@@ skipping 188 matching lines @@
                                  SubMessagePrefix(prefix, field, -1),
                                  errors);
       }
     }
   }
 }
 
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google