Read compositor VSync information from platform, when possible

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index d3357f0df5d87c81ae5f1cf6a2a640348462ceea..324a20d64f1aba4b1d69fa8c75a48d87837dcd15 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -3214,7 +3214,6 @@ void RenderWidgetHostViewAura::OnCompositingLockStateChanged(
 }
 
 void RenderWidgetHostViewAura::OnUpdateVSyncParameters(
-    ui::Compositor* compositor,
     base::TimeTicks timebase,
     base::TimeDelta interval) {
   if (IsShowing()) {
@@ -3511,6 +3510,10 @@ void RenderWidgetHostViewAura::AddedToRootWindow() {
     if (input_method)
       input_method->SetFocusedTextInputClient(this);
   }
+
+  ui::Compositor* compositor = GetCompositor();
+  if (compositor)
+    compositor->vsync_manager()->AddObserver(this);

[sheu, 2014/02/04 03:23:21]

Not sure where I should be adding and removing this as an observer as the vsync
manager, that would guarantee that we don't miss an add/remove.

[piman, 2014/02/04 04:51:01]

This is I think the right place.

 }
 
 void RenderWidgetHostViewAura::RemovingFromRootWindow() {
@@ -3535,8 +3538,11 @@ void RenderWidgetHostViewAura::RemovingFromRootWindow() {
   RunOnCommitCallbacks();
   resize_lock_.reset();
   host_->WasResized();
-  if (compositor && compositor->HasObserver(this))
-    compositor->RemoveObserver(this);
+  if (compositor) {
+    if (compositor->HasObserver(this))
+      compositor->RemoveObserver(this);
+    compositor->vsync_manager()->RemoveObserver(this);

[sheu, 2014/02/04 03:23:21]

See above.

[piman, 2014/02/04 04:51:01]

Here too.

+  }
 }
 
 ui::Compositor* RenderWidgetHostViewAura::GetCompositor() const {