Added a command line flag that disables force-compositing-mode and modified the about:flags entry t…

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 174 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
 
+  // 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,
         "disable", 2012, 12, 31, NULL));
 
   // Produce the same result on every run of this client.
   trial->UseOneTimeRandomization();
   // 50% probability of being in the enabled group.
   const base::FieldTrial::Probability kEnableProbability = 50;
@@ skipping 157 matching lines @@
         status = "enabled";
         if (kGpuFeatureInfo[i].name == "webgl" &&
             (command_line.HasSwitch(switches::kDisableAcceleratedCompositing) ||
              (flags & content::GPU_FEATURE_TYPE_ACCELERATED_COMPOSITING)))
           status += "_readback";
         bool has_thread =
             command_line.HasSwitch(switches::kEnableThreadedCompositing) &&
             !command_line.HasSwitch(switches::kDisableThreadedCompositing);
         if (kGpuFeatureInfo[i].name == "compositing") {
           bool force_compositing =
-              command_line.HasSwitch(switches::kForceCompositingMode) ||
+              (command_line.HasSwitch(switches::kForceCompositingMode) &&
+               !command_line.HasSwitch(
+                   switches::kDisableForceCompositingMode)) ||
               InForceCompositingModeTrial();
           if (force_compositing)
             status += "_force";
           if (has_thread)
             status += "_threaded";
         }
         if (kGpuFeatureInfo[i].name == "css_animation") {
           if (has_thread)
             status = "accelerated_threaded";
           else
@@ skipping 182 matching lines @@
         kGpuBlacklistFeatureHistogramNamesWin[i],
         1, kNumWinSubVersions * kGpuFeatureNumStatus,
         kNumWinSubVersions * kGpuFeatureNumStatus + 1,
         base::Histogram::kUmaTargetedHistogramFlag);
     histogram_pointer->Add(GetGpuBlacklistHistogramValueWin(value));
 #endif
   }
 }
 
 }  // namespace gpu_util;