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

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
===================================================================
--- chrome/browser/chrome_content_browser_client.cc	(revision 140632)
+++ chrome/browser/chrome_content_browser_client.cc	(working copy)
@@ -10,11 +10,13 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/metrics/histogram.h"
 #include "base/string_tokenizer.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/app/breakpad_mac.h"
 #include "chrome/browser/browser_about_handler.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/browser_trial.h"
 #include "chrome/browser/browsing_data_helper.h"
 #include "chrome/browser/browsing_data_remover.h"
 #include "chrome/browser/character_encoding.h"
@@ -75,6 +77,7 @@
 #include "chrome/common/child_process_logging.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/chrome_version_info.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_process_policy.h"
 #include "chrome/common/extensions/extension_set.h"
@@ -104,8 +107,10 @@
 #include "webkit/plugins/plugin_switches.h"
 
 #if defined(OS_WIN)
+#include "base/win/windows_version.h"
 #include "chrome/browser/chrome_browser_main_win.h"
 #elif defined(OS_MACOSX)
+#include "base/mac/mac_util.h"
 #include "chrome/browser/chrome_browser_main_mac.h"
 #include "chrome/browser/spellchecker/spellcheck_message_filter_mac.h"
 #elif defined(OS_CHROMEOS)
@@ -307,6 +312,43 @@
   }
 }
 
+void CheckForceCompositingModeTrialFlag(CommandLine* command_line) {
+  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
+  // Only run the trial on the Canary channel.
+  if (channel != chrome::VersionInfo::CHANNEL_CANARY)
+    return;
+#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
+
+  static base::FieldTrial* trial = NULL;
+  static bool in_enable_group = false;
+
+  if (!trial) {
+    const base::FieldTrial::Probability kDivisor = 100;
+    // 50% probability of being in the enabled group.
+    const base::FieldTrial::Probability kEnableProbability = 50;
+    trial = base::FieldTrialList::FactoryGetFieldTrial(
+        BrowserTrial::kForceCompositingModeTrial, kDivisor,
+        "disable", 2012, 12, 31, NULL);
+    // Produce the same result on every run of this client.
+    trial->UseOneTimeRandomization();
+    int enable_group = trial->AppendGroup("enable", kEnableProbability);
+    in_enable_group = (trial->group() == enable_group);
+    UMA_HISTOGRAM_ENUMERATION("GPU.InForceCompositingModeFieldTrial",

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

nit: UMA_HISTOGRAM_BOOLEAN?

+                              in_enable_group ? 1 : 0, 2);
+  }
+
+  if (in_enable_group)
+    command_line->AppendSwitch(switches::kForceCompositingMode);
+}
+
 }  // namespace
 
 namespace chrome {
@@ -751,6 +793,8 @@
       }
     }
 
+    CheckForceCompositingModeTrialFlag(command_line);
+
     // Please keep this in alphabetical order.
     static const char* const kSwitchNames[] = {
       switches::kAllowHTTPBackgroundPage,