Add threaded compositing mode to field trial

content/public/common/content_constants.cc

 // Copyright (c) 2012 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 "content/public/common/content_constants.h"
 namespace content {
 
 const FilePath::CharType kAppCacheDirname[] =
     FILE_PATH_LITERAL("Application Cache");
 const FilePath::CharType kPepperDataDirname[] =
@@ skipping 14 matching lines @@
 #else
 const wchar_t kBrowserAppName[] = L"Chromium";
 const char    kStatsFilename[] = "ChromiumStats2";
 #endif
 
 const int kStatsMaxThreads = 32;
 const int kStatsMaxCounters = 3000;
 
 const int kHistogramSynchronizerReservedSequenceNumber = 0;
 
+const char kGpuCompositingFieldTrialName[] = "ForceCompositingMode";
+const char kGpuCompositingFieldTrialEnabledName[] = "enabled";
+const char kGpuCompositingFieldTrialThreadEnabledName[] = "thread";
+
 }  // namespace content