Add missing IWYU message_loop.h includes.

google_apis/gcm/base/socket_stream_unittest.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/base/socket_stream.h"
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_piece.h"
 #include "net/base/ip_address.h"
 #include "net/log/net_log_source.h"
 #include "net/socket/socket_test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace gcm {
 namespace {
 
@@ skipping 370 matching lines @@
 TEST_F(GCMSocketStreamTest, WriteDisconnected) {
   BuildSocket(ReadList(), WriteList());
   socket()->Disconnect();
   DoOutputStreamWrite(base::StringPiece(kWriteData, kWriteDataSize));
   ASSERT_EQ(SocketOutputStream::CLOSED, output_stream()->GetState());
   ASSERT_EQ(net::ERR_CONNECTION_CLOSED, output_stream()->last_error());
 }
 
 }  // namespace
 }  // namespace gcm