Adding a field trial for testing --force-compositing-mode on 50% of

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"
 #include "base/metrics/histogram.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/sys_info.h"
 #include "base/values.h"
 #include "base/version.h"
+#include "chrome/browser/browser_trial.h"
 #include "chrome/browser/gpu_blacklist.h"
 #include "content/public/browser/gpu_data_manager.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/gpu_info.h"
 
 using content::GpuDataManager;
 using content::GpuFeatureType;
 
 namespace {
 
@@ skipping 169 matching lines @@
     if (type & content::GPU_FEATURE_TYPE_FLASH3D)
       matches.push_back(kGpuFeatureNameFlash3d);
     if (type & content::GPU_FEATURE_TYPE_FLASH_STAGE3D)
       matches.push_back(kGpuFeatureNameFlashStage3d);
     if (!matches.size())
       matches.push_back(kGpuFeatureNameUnknown);
   }
   return JoinString(matches, ',');
 }
 
+bool InForceCompositingFieldTrial() {

[SteveT, 2012/06/06 13:06:02]

nit: Indent is 4 here instead of 2.

+    base::FieldTrial* trial =
+        base::FieldTrialList::Find(BrowserTrial::kForceCompositingModeTrial);
+    if (!trial)
+      return false;

[Ilya Sherman, 2012/06/06 09:50:21]

Can this be a DCHECK rather than an if-stmt?  (See comment below for
motivation.)

+    if (trial->group_name() != std::string("enable"))

[Ilya Sherman, 2012/06/06 09:50:21]

nit: return trial->group_name() == "enable";

+      return false;
+
+    return true;
+}
+
 Value* GetFeatureStatus() {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
   bool gpu_access_blocked = !GpuDataManager::GetInstance()->GpuAccessAllowed();
 
   uint32 flags = GpuDataManager::GetInstance()->GetGpuFeatureType();
   DictionaryValue* status = new DictionaryValue();
 
   const GpuFeatureInfo kGpuFeatureInfo[] = {
       {
           "2d_canvas",
@@ skipping 91 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 = CommandLine::ForCurrentProcess()->HasSwitch(
             switches::kEnableThreadedCompositing) &&
             (!CommandLine::ForCurrentProcess()->HasSwitch(
                 switches::kDisableThreadedCompositing));
         if (kGpuFeatureInfo[i].name == "compositing" &&
-            CommandLine::ForCurrentProcess()->HasSwitch(
-                switches::kForceCompositingMode))
+            (CommandLine::ForCurrentProcess()->HasSwitch(
+                 switches::kForceCompositingMode) ||
+             InForceCompositingFieldTrial()))

[Ilya Sherman, 2012/06/06 09:50:21]

Will the field trial always be set up by the time this code is reached?  If not,
is it ok that this function might return different results depending on when it
is called?

           status += "_force";
         if (kGpuFeatureInfo[i].name == "compositing" &&
             has_thread)
           status += "_threaded";
         if (kGpuFeatureInfo[i].name == "css_animation") {
           if (has_thread)
             status = "accelerated_threaded";
           else
             status = "accelerated";
         }
@@ skipping 180 matching lines @@
         kGpuBlacklistFeatureHistogramNamesWin[i],
         1, kNumWinSubVersions * kGpuFeatureNumStatus,
         kNumWinSubVersions * kGpuFeatureNumStatus + 1,
         base::Histogram::kUmaTargetedHistogramFlag);
     histogram_pointer->Add(GetGpuBlacklistHistogramValueWin(value));
 #endif
   }
 }
 
 }  // namespace gpu_util;