Mac Overlays: Add GPU back-pressure

ui/accelerated_widget_mac/display_link_mac.h

Index: ui/accelerated_widget_mac/display_link_mac.h
diff --git a/ui/accelerated_widget_mac/display_link_mac.h b/ui/accelerated_widget_mac/display_link_mac.h
index 1ec7a7200cf3528ce11a428e32ac11c4efeda6fa..e462e28bc15eefe39e2ba8efb07ec5b28a6c6cef 100644
--- a/ui/accelerated_widget_mac/display_link_mac.h
+++ b/ui/accelerated_widget_mac/display_link_mac.h
@@ -5,8 +5,8 @@
 #ifndef UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 #define UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 
-#include <QuartzCore/CVDisplayLink.h>
 #include <map>
+#include <QuartzCore/CVDisplayLink.h>
 
 #include "base/lazy_instance.h"
 #include "base/mac/scoped_typeref.h"
@@ -24,11 +24,19 @@ class ACCELERATED_WIDGET_MAC_EXPORT DisplayLinkMac :
   static scoped_refptr<DisplayLinkMac> GetForDisplay(
       CGDirectDisplayID display_id);
 
+  CGDirectDisplayID display_id() const { return display_id_; }
+
   // Get vsync scheduling parameters.
   bool GetVSyncParameters(
       base::TimeTicks* timebase,
       base::TimeDelta* interval);
 
+  // Return the time of |interval_fraction| of the way through the next
+  // vsync period that starts after |from|. If the vsync parameters have
+  // not yet been computed, return |from|.
+  base::TimeTicks GetNextVSyncTimeAfter(
+      const base::TimeTicks& from, double interval_fraction);
+
  private:
   friend class base::RefCounted<DisplayLinkMac>;
 
@@ -70,6 +78,7 @@ class ACCELERATED_WIDGET_MAC_EXPORT DisplayLinkMac :
   // VSync parameters computed during Tick.
   bool timebase_and_interval_valid_;
   base::TimeTicks timebase_;
+  base::TimeTicks timebase_remainder_;
   base::TimeDelta interval_;
 
   // Each display link instance consumes a non-negligible number of cycles, so