Mac Overlays: Add GPU back-pressure

ui/accelerated_widget_mac/accelerated_widget_mac.mm

Index: ui/accelerated_widget_mac/accelerated_widget_mac.mm
diff --git a/ui/accelerated_widget_mac/accelerated_widget_mac.mm b/ui/accelerated_widget_mac/accelerated_widget_mac.mm
index 82390e5d6b93005fa28da5bc69a024f451282c16..954c2764165dce4e04f93c525278981104caef05 100644
--- a/ui/accelerated_widget_mac/accelerated_widget_mac.mm
+++ b/ui/accelerated_widget_mac/accelerated_widget_mac.mm
@@ -110,6 +110,12 @@ int AcceleratedWidgetMac::GetRendererID() const {
   return 0;
 }
 
+uint32_t AcceleratedWidgetMac::GetDisplayID() const {
+  if (view_)
+    return view_->AcceleratedWidgetGetDisplayID();

[tapted, 2015/08/05 07:55:57]

is this always the same as

[[[[[AcceleratedWidgetGetNSView() window] screen] deviceDescription]
objectForKey:@"NSScreenNumber"] intValue];

(not suggesting we use that - but it might be something to use in
BridgedNativeWidgdet)

[ccameron, 2015/08/05 21:00:43]

Almost always -- the display_id can be set to 0 if vsync is to be disabled. I'll
update the method name to include that detail.

+  return 0;
+}
+
 bool AcceleratedWidgetMac::IsRendererThrottlingDisabled() const {
   if (view_)
     return view_->AcceleratedWidgetShouldIgnoreBackpressure();
@@ -365,7 +371,7 @@ void AcceleratedWidgetMacGotAcceleratedFrame(
     float scale_factor,
     const gfx::Rect& pixel_damage_rect,
     const base::Closure& drawn_callback,
-    bool* disable_throttling, int* renderer_id) {
+    bool* disable_throttling, int* renderer_id, uint32_t* display_id) {
   AcceleratedWidgetMac* accelerated_widget_mac =
       GetHelperFromAcceleratedWidget(widget);
   if (accelerated_widget_mac) {
@@ -375,9 +381,11 @@ void AcceleratedWidgetMacGotAcceleratedFrame(
     *disable_throttling =
         accelerated_widget_mac->IsRendererThrottlingDisabled();
     *renderer_id = accelerated_widget_mac->GetRendererID();
+    *display_id = accelerated_widget_mac->GetDisplayID();
   } else {
     *disable_throttling = false;
     *renderer_id = 0;
+    *display_id = 0;
   }
 }