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..b15842f3da8d1f10b46a89b60b4f9b75c37f3ab3 100644
--- a/content/browser/gpu/gpu_data_manager_impl_private.cc
+++ b/content/browser/gpu/gpu_data_manager_impl_private.cc
@@ -241,7 +241,9 @@ void DisplayReconfigCallback(CGDirectDisplayID display,
 
   bool fireGpuSwitch = flags & kCGDisplayAddFlag;
 
-  if (displayCount != manager->GetDisplayCount()) {
+  if(manager->IsDriverBugWorkaroundActive(
+      gpu::DISABLE_MULTIMONITOR_MULTISAMPLING) &&
+      displayCount != manager->GetDisplayCount()) {

[Ken Russell (switch to Gerrit), 2013/08/29 19:28:00]

The workaround check needs to be done below in order to handle the situation
where a GPU switch event is fired for unrelated reasons. I think it would be
better to remove the check here, even though we'll be firing a GPU switch event
that has no effect.

     manager->SetDisplayCount(displayCount);
     fireGpuSwitch = true;
   }
@@ -376,6 +378,10 @@ 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;