Read compositor VSync information from platform, when possible

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 46050fedd83951496539f78f0dd91cf271f7e58b..456609152e8f405e79f0bb6eb76507c64b2adced 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -27,6 +27,7 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/compositor/compositor_observer.h"
 #include "ui/compositor/compositor_switches.h"
+#include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/compositor/dip_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/gfx/frame_time.h"
@@ -183,6 +184,7 @@ namespace ui {
 Compositor::Compositor(gfx::AcceleratedWidget widget)
     : root_layer_(NULL),
       widget_(widget),
+      vsync_manager_(new CompositorVSyncManager()),
       posted_swaps_(new PostedSwapQueue()),
       device_scale_factor_(0.0f),
       last_started_frame_(0),
@@ -417,6 +419,10 @@ void Compositor::SetBackgroundColor(SkColor color) {
   ScheduleDraw();
 }
 
+scoped_refptr<CompositorVSyncManager> Compositor::vsync_manager() const {
+  return vsync_manager_;
+}
+
 void Compositor::AddObserver(CompositorObserver* observer) {
   observer_list_.AddObserver(observer);
 }
@@ -429,13 +435,6 @@ bool Compositor::HasObserver(CompositorObserver* observer) {
   return observer_list_.HasObserver(observer);
 }
 
-void Compositor::OnUpdateVSyncParameters(base::TimeTicks timebase,
-                                         base::TimeDelta interval) {
-  FOR_EACH_OBSERVER(CompositorObserver,
-                    observer_list_,
-                    OnUpdateVSyncParameters(this, timebase, interval));
-}
-
 void Compositor::Layout() {
   // We're sending damage that will be addressed during this composite
   // cycle, so we don't need to schedule another composite to address it.