Always enable FCM on Windows.

chrome/browser/gpu/chrome_gpu_util.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 "chrome/browser/gpu/chrome_gpu_util.h"
 
 #include "base/command_line.h"
 #if defined(OS_MACOSX)
 #include "base/mac/mac_util.h"
 #endif
@@ skipping 22 matching lines @@
   if (trial)
     trial->Disable();
 }
 
 bool ShouldRunCompositingFieldTrial() {
 // Enable the field trial only on desktop OS's.
 #if !(defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX))
   return false;
 #endif
 
-// Necessary for linux_chromeos build since it defines both OS_LINUX
-// and OS_CHROMEOS.
-#if defined(OS_CHROMEOS)
-  return false;
-#endif
-
-#if defined(OS_WIN)
-  // Don't run the trial on Windows XP.
-  if (base::win::GetVersion() < base::win::VERSION_VISTA)
-    return false;
-#endif
-
 #if defined(OS_MACOSX)
   // Browser and content shell tests hang on 10.7 when the Apple software
   // renderer is used. These tests ignore the blacklist (which disables
   // compositing both on 10.7 and when the Apple software renderer is used)
   // by specifying the kSkipGpuDataLoading switch, so disable forced
   // compositing here based on the switch and OS version.
   // http://crbug.com/230931
   if (base::mac::IsOSLion() &&
       CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kSkipGpuDataLoading)) {
@@ skipping 58 matching lines @@
 
   bool force_compositing = (trial->group() == force_compositing_group);
   bool thread = (trial->group() == thread_group);
   UMA_HISTOGRAM_BOOLEAN("GPU.InForceCompositingModeFieldTrial",
                         force_compositing);
   UMA_HISTOGRAM_BOOLEAN("GPU.InCompositorThreadFieldTrial", thread);
 }
 
 }  // namespace gpu_util