Mac Overlays: Add GPU back-pressure

ui/accelerated_widget_mac/display_link_mac.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 #define UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_
 
+#include <map>
 #include <QuartzCore/CVDisplayLink.h>
-#include <map>
 
 #include "base/lazy_instance.h"
 #include "base/mac/scoped_typeref.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "ui/accelerated_widget_mac/accelerated_widget_mac_export.h"
 
 namespace ui {
 
 class ACCELERATED_WIDGET_MAC_EXPORT DisplayLinkMac :
     public base::RefCounted<DisplayLinkMac> {
  public:
   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>;
 
   DisplayLinkMac(
       CGDirectDisplayID display_id,
       base::ScopedTypeRef<CVDisplayLinkRef> display_link);
   virtual ~DisplayLinkMac();
 
   void StartOrContinueDisplayLink();
   void StopDisplayLink();
@@ skipping 21 matching lines @@
 
   // The display that this display link is attached to.
   CGDirectDisplayID display_id_;
 
   // CVDisplayLink for querying VSync timing info.
   base::ScopedTypeRef<CVDisplayLinkRef> display_link_;
 
   // 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
   // make all display links on the same screen share the same object.
   typedef std::map<CGDirectDisplayID, DisplayLinkMac*> DisplayMap;
   static base::LazyInstance<DisplayMap> display_map_;
 };
 
 }  // ui
 
 #endif  // UI_ACCELERATED_WIDGET_MAC_DISPLAY_LINK_MAC_H_