Updated OSX to blacklist multisampling when multiple monitors are connected

content/browser/gpu/gpu_data_manager_impl.cc

Index: content/browser/gpu/gpu_data_manager_impl.cc
diff --git a/content/browser/gpu/gpu_data_manager_impl.cc b/content/browser/gpu/gpu_data_manager_impl.cc
index 1ac0c173c13c6c67c79d3c52fd42ac25e2fe51f5..d8a3ed4edba1311b19e18298ff198d57d67ff9da 100644
--- a/content/browser/gpu/gpu_data_manager_impl.cc
+++ b/content/browser/gpu/gpu_data_manager_impl.cc
@@ -78,12 +78,25 @@ std::string IntSetToString(const std::set<int>& list) {
 void DisplayReconfigCallback(CGDirectDisplayID display,
                              CGDisplayChangeSummaryFlags flags,
                              void* gpu_data_manager) {
-  if (flags & kCGDisplayAddFlag) {
-    GpuDataManagerImpl* manager =
-        reinterpret_cast<GpuDataManagerImpl*>(gpu_data_manager);
-    DCHECK(manager);
-    manager->HandleGpuSwitch();
+  if(flags == kCGDisplayBeginConfigurationFlag)
+    return; // This call contains no information about the display change
+
+  GpuDataManagerImpl* manager =
+      reinterpret_cast<GpuDataManagerImpl*>(gpu_data_manager);
+  DCHECK(manager);
+
+  uint32_t displayCount;
+  CGGetActiveDisplayList(0, NULL, &displayCount);
+
+  bool fireGpuSwitch = flags & kCGDisplayAddFlag;
+
+  if (displayCount != manager->display_count_) {
+    manager->display_count_ = displayCount;
+    fireGpuSwitch = true;
   }
+
+  if (fireGpuSwitch)
+    manager->HandleGpuSwitch();
 }
 #endif  // OS_MACOSX
 
@@ -558,7 +571,8 @@ void GpuDataManagerImpl::UpdateRendererWebPrefs(WebPreferences* prefs) const {
     prefs->flash_stage3d_baseline_enabled = false;
   if (IsFeatureBlacklisted(GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS))
     prefs->accelerated_2d_canvas_enabled = false;
-  if (IsFeatureBlacklisted(GPU_FEATURE_TYPE_MULTISAMPLING))
+  if (IsFeatureBlacklisted(GPU_FEATURE_TYPE_MULTISAMPLING)
+      || display_count_ > 1)
     prefs->gl_multisampling_enabled = false;
   if (IsFeatureBlacklisted(GPU_FEATURE_TYPE_3D_CSS)) {
     prefs->accelerated_compositing_for_3d_transforms_enabled = false;
@@ -712,6 +726,7 @@ GpuDataManagerImpl::GpuDataManagerImpl()
   }
 
 #if defined(OS_MACOSX)
+  CGGetActiveDisplayList (0, NULL, &display_count_);
   CGDisplayRegisterReconfigurationCallback(DisplayReconfigCallback, this);
 #endif  // OS_MACOSX
 }