[GCM] Add support for canary connection attempts

google_apis/gcm/engine/connection_handler_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "google_apis/gcm/engine/connection_handler_impl.h"
 
 #include "base/message_loop/message_loop.h"
 #include "google/protobuf/io/coded_stream.h"
 #include "google_apis/gcm/base/mcs_util.h"
 #include "google_apis/gcm/base/socket_stream.h"
@@ skipping 384 matching lines @@
   CloseConnection();
   connection_callback_.Run(net::ERR_TIMED_OUT);
 }
 
 void ConnectionHandlerImpl::CloseConnection() {
   DVLOG(1) << "Closing connection.";
   read_timeout_timer_.Stop();
   if (socket_)
     socket_->Disconnect();
   socket_ = NULL;
+  handshake_complete_ = false;
+  message_tag_ = 0;
+  message_size_ = 0;
   input_stream_.reset();
   output_stream_.reset();
   weak_ptr_factory_.InvalidateWeakPtrs();
 }
 
 }  // namespace gcm