Change LayerHostImpl to use frame time from BeginFrameArgs rather than ::Now()

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index ae3a4217c6507a35e881cbae55140d1f767a6e37..c1fb010c1bf21c59c36f9f038ae03565f58fe7b8 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -255,8 +255,8 @@ void LayerTreeImpl::SetCurrentlyScrollingLayer(LayerImpl* layer) {
 
   if (currently_scrolling_layer_ &&
       currently_scrolling_layer_->scrollbar_animation_controller())
-    currently_scrolling_layer_->scrollbar_animation_controller()->
-        DidScrollGestureEnd(CurrentPhysicalTimeTicks());
+    currently_scrolling_layer_->scrollbar_animation_controller()
+        ->DidScrollGestureEnd(CurrentFrameTimeTicks());

[aelias_OOO_until_Jul13, 2014/03/21 01:37:44]

physical time.  Note that I specifically changed this line from frame time to
physical time to fix a regression in this patch:
https://chromiumcodereview.appspot.com/16925007

   currently_scrolling_layer_ = layer;
   if (layer && layer->scrollbar_animation_controller())
     layer->scrollbar_animation_controller()->DidScrollGestureBegin();
@@ -682,10 +682,6 @@ base::TimeTicks LayerTreeImpl::CurrentFrameTimeTicks() const {
   return layer_tree_host_impl_->CurrentFrameTimeTicks();
 }
 
-base::TimeTicks LayerTreeImpl::CurrentPhysicalTimeTicks() const {
-  return layer_tree_host_impl_->CurrentPhysicalTimeTicks();
-}
-
 void LayerTreeImpl::SetNeedsCommit() {
   layer_tree_host_impl_->SetNeedsCommit();
 }