Add LayerTreeHostSettings for synchronous compositor

cc/scheduler/vsync_time_source.h

 // Copyright 2013 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 CC_SCHEDULER_VSYNC_TIME_SOURCE_H_
 #define CC_SCHEDULER_VSYNC_TIME_SOURCE_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/scheduler/time_source.h"
 
@@ skipping 15 matching lines @@
   virtual void RequestVSyncNotification(VSyncClient* client) = 0;
 
  protected:
   virtual ~VSyncProvider() {}
 };
 
 // This timer implements a time source that is explicitly triggered by an
 // external vsync signal.
 class CC_EXPORT VSyncTimeSource : public TimeSource, public VSyncClient {
  public:
-  static scoped_refptr<VSyncTimeSource> Create(VSyncProvider* vsync_provider);
+  enum NotificationDisableOption {
+    // The notification will be lazily disabled in the callback to ensure
+    // we get notified of the frame immediately following a quick on-off-on
+    // transition.
+    DISABLE_ON_NEXT_TICK,
+    DISABLE_SYNCHRONOUSLY
+  };
+
+  static scoped_refptr<VSyncTimeSource> Create(
+      VSyncProvider* vsync_provider, NotificationDisableOption option);
 
   // TimeSource implementation
   virtual void SetClient(TimeSourceClient* client) OVERRIDE;
   virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
                                       base::TimeDelta interval) OVERRIDE;
   virtual void SetActive(bool active) OVERRIDE;
   virtual bool Active() const OVERRIDE;
   virtual base::TimeTicks LastTickTime() OVERRIDE;
   virtual base::TimeTicks NextTickTime() OVERRIDE;
 
   // VSyncClient implementation
   virtual void DidVSync(base::TimeTicks frame_time) OVERRIDE;
 
  protected:
-  explicit VSyncTimeSource(VSyncProvider* vsync_provider);
+  explicit VSyncTimeSource(VSyncProvider* vsync_provider,
+                           NotificationDisableOption option);
   virtual ~VSyncTimeSource();
 
   base::TimeTicks last_tick_time_;
   base::TimeDelta interval_;
   bool active_;
   bool notification_requested_;
 
   VSyncProvider* vsync_provider_;
   TimeSourceClient* client_;
+  NotificationDisableOption disable_option_;
 
   DISALLOW_COPY_AND_ASSIGN(VSyncTimeSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_VSYNC_TIME_SOURCE_H_