Disable threaded compositing field trial on mac and linux

This flag is not feature complete on mac and linux, it's premature to enable field trials.

BUG=133602,140866


Review URL: https://chromiumcodereview.appspot.com/10824271

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151182 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/gpu_util.cc

@@ -220,11 +220,19 @@ void InitializeCompositingFieldTrial() {
     // 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);