Enable by default threaded compositing on windows and FCM on mac

chrome/browser/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/chrome_gpu_util.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/version.h"
@@ skipping 53 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
 
   // The performance of accelerated compositing is too low with software
   // rendering.
   if (content::GpuDataManager::GetInstance()->ShouldUseSoftwareRendering())
     return false;
@@ skipping 15 matching lines @@
 // trial must call DisableCompositingFieldTrial() before returning.
 void InitializeCompositingFieldTrial() {
   // Early out in configurations that should not run the compositing
   // field trial.
   if (!ShouldRunCompositingFieldTrial()) {
     DisableCompositingFieldTrial();
     return;
   }
 
   const base::FieldTrial::Probability kDivisor = 3;
+  // Note: This field trial should be removed once we're comfortable with
+  // turning force compositing mode and threaded compositing on all relevant
+  // platforms (see crbug.com/149991).
   scoped_refptr<base::FieldTrial> trial(
     base::FieldTrialList::FactoryGetFieldTrial(
         content::kGpuCompositingFieldTrialName, kDivisor,
-        "disable", 2012, 12, 31, NULL));
+        "disable", 2013, 12, 31, NULL));
 
   // Produce the same result on every run of this client.
   trial->UseOneTimeRandomization();
 
+  // Note: The static field trial probabilities set here can be overwritten
+  // at runtime by Finch. Changing these static values won't have an effect
+  // if a Finch study is active.
   base::FieldTrial::Probability force_compositing_mode_probability = 0;
   base::FieldTrial::Probability threaded_compositing_probability = 0;
 
+  // Threaded compositing mode isn't feature complete on mac or linux yet:
+  // http://crbug.com/133602 for mac
+  // http://crbug.com/140866 for linux
+
+#if defined(OS_WIN)
+  // threaded-compositing turned on by default on Windows.
+  // (Windows XP is excluded explicitly in ShouldRunCompositingFieldTrial)
+  threaded_compositing_probability = 3;
+#elif defined(OS_LINUX) || defined(OS_MACOSX)
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
-  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
-      channel == chrome::VersionInfo::CHANNEL_BETA) {
-    // Stable and Beta channels: Non-threaded force-compositing-mode on by
-    // default (mac and windows only).
-#if defined(OS_WIN) || defined(OS_MACOSX)
-    force_compositing_mode_probability = 3;
+  if (channel != chrome::VersionInfo::CHANNEL_STABLE &&
+      channel != chrome::VersionInfo::CHANNEL_BETA) {
+    // On channels < beta, force-compositing-mode on
+    // with 33% probability.
+    force_compositing_mode_probability = 1;
+  }
 #endif
-  } else if (channel == chrome::VersionInfo::CHANNEL_DEV ||
-             channel == chrome::VersionInfo::CHANNEL_CANARY) {
-    // Dev and Canary channels: force-compositing-mode and
-    // threaded-compositing on with 1/3 probability each.
-    force_compositing_mode_probability = 1;
-
-#if defined(OS_MACOSX) || defined(OS_LINUX)
-    // Threaded compositing mode isn't feature complete on mac or linux yet:
-    // http://crbug.com/133602 for mac
-    // http://crbug.com/140866 for linux
-    threaded_compositing_probability = 0;
-#else
-    if (!CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kDisableThreadedCompositing))
-        threaded_compositing_probability = 1;
-#endif
-  }
 
   int force_compositing_group = trial->AppendGroup(
       content::kGpuCompositingFieldTrialForceCompositingEnabledName,
       force_compositing_mode_probability);
   int thread_group = trial->AppendGroup(
       content::kGpuCompositingFieldTrialThreadEnabledName,
       threaded_compositing_probability);
 
   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;