Disable force-compositing-mode experiment when using swiftshader.

chrome/browser/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_util.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
@@ skipping 175 matching lines @@
 #if defined(OS_WIN)
   // Don't run the trial on Windows XP.
   if (base::win::GetVersion() < base::win::VERSION_VISTA)
     return;
 #elif defined(OS_MACOSX)
   // Accelerated compositing is only implemented on Mac OSX 10.6 or later.
   if (base::mac::IsOSLeopardOrEarlier())
     return;
 #endif
 
+  // The performance of accelerated compositing is too low with software
+  // rendering.
+  if (content::GpuDataManager::GetInstance()->ShouldUseSoftwareRendering())
+    return;
+
   // Don't activate the field trial if force-compositing-mode has been
   // explicitly disabled from the command line.
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableForceCompositingMode))
     return;
 
   const base::FieldTrial::Probability kDivisor = 100;
   scoped_refptr<base::FieldTrial> trial(
     base::FieldTrialList::FactoryGetFieldTrial(
         kForceCompositingModeFieldTrialName, kDivisor,
@@ skipping 368 matching lines @@
         kGpuBlacklistFeatureHistogramNamesWin[i],
         1, kNumWinSubVersions * kGpuFeatureNumStatus,
         kNumWinSubVersions * kGpuFeatureNumStatus + 1,
         base::Histogram::kUmaTargetedHistogramFlag);
     histogram_pointer->Add(GetGpuBlacklistHistogramValueWin(value));
 #endif
   }
 }
 
 }  // namespace gpu_util;