Added GPU driver workaround for OSX multimonitor multisampling disabling

content/browser/gpu/gpu_data_manager_impl_private.cc

Index: content/browser/gpu/gpu_data_manager_impl_private.cc
diff --git a/content/browser/gpu/gpu_data_manager_impl_private.cc b/content/browser/gpu/gpu_data_manager_impl_private.cc
index 98656dfdd68ccffbf7f02be7ae4f9f663d753a74..ed768a044cfe3dad18d1e9544843e140728b3150 100644
--- a/content/browser/gpu/gpu_data_manager_impl_private.cc
+++ b/content/browser/gpu/gpu_data_manager_impl_private.cc
@@ -241,7 +241,7 @@ void DisplayReconfigCallback(CGDirectDisplayID display,
 
   bool fireGpuSwitch = flags & kCGDisplayAddFlag;
 
-  if (displayCount != manager->GetDisplayCount()) {
+  if(displayCount != manager->GetDisplayCount()) {

[Ken Russell (switch to Gerrit), 2013/08/29 21:05:05]

Please undo this whitespace change.

     manager->SetDisplayCount(displayCount);
     fireGpuSwitch = true;
   }
@@ -376,6 +376,10 @@ bool GpuDataManagerImplPrivate::IsFeatureBlacklisted(int feature) const {
   return (blacklisted_features_.count(feature) == 1);
 }
 
+bool GpuDataManagerImplPrivate::IsDriverBugWorkaroundActive(int feature) const {
+  return (gpu_driver_bugs_.count(feature) == 1);
+}
+
 size_t GpuDataManagerImplPrivate::GetBlacklistedFeatureCount() const {
   if (use_swiftshader_)
     return 1;
@@ -817,8 +821,9 @@ void GpuDataManagerImplPrivate::UpdateRendererWebPrefs(
     prefs->flash_stage3d_baseline_enabled = false;
   if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS))
     prefs->accelerated_2d_canvas_enabled = false;
-  if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_MULTISAMPLING)
-      || display_count_ > 1)
+  if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_MULTISAMPLING) ||
+      (IsDriverBugWorkaroundActive(gpu::DISABLE_MULTIMONITOR_MULTISAMPLING) &&
+          display_count_ > 1))
     prefs->gl_multisampling_enabled = false;
   if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_3D_CSS)) {
     prefs->accelerated_compositing_for_3d_transforms_enabled = false;