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

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index d4c48f9c9e624fc1ce5309d4f45251aee8e12260..3101eba4ca0cb9554f3f20247245ad2da3781a18 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -167,12 +167,15 @@ class LayerTreeHostImplTimeSourceAdapter : public TimeSourceClient {
       layer_tree_host_impl_->ManageTiles();
     }
 
+    // TODO(mithro): Change to using something like
+    // OnBackgroundFrame(BeginFrameArgs xxx)
+    layer_tree_host_impl_->OverrideCurrentFrameTime(

[danakj, 2014/03/11 18:32:36]

This should be above UpdateDrawProps/ManageTiles.

+        time_source_->LastTickTime());
     layer_tree_host_impl_->Animate(
         layer_tree_host_impl_->CurrentFrameTimeTicks());
     layer_tree_host_impl_->UpdateBackgroundAnimateTicking(true);
     bool start_ready_animations = true;
     layer_tree_host_impl_->UpdateAnimationState(start_ready_animations);
-    layer_tree_host_impl_->ResetCurrentFrameTimeForNextFrame();
   }
 
   void SetActive(bool active) {
@@ -1290,6 +1293,9 @@ void LayerTreeHostImpl::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
 }
 
 void LayerTreeHostImpl::BeginImplFrame(const BeginFrameArgs& args) {
+  last_frame_args_ = current_frame_args_;
+  current_frame_args_ = args;
+
   client_->BeginImplFrame(args);
 }
 
@@ -2470,8 +2476,7 @@ void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
         scroll_layer_impl ? scroll_layer_impl->scrollbar_animation_controller()
                           : NULL;
     if (animation_controller) {
-      animation_controller->DidMouseMoveOffScrollbar(
-          CurrentPhysicalTimeTicks());
+      animation_controller->DidMouseMoveOffScrollbar(CurrentFrameTimeTicks());

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

physical time

       StartScrollbarAnimation();
     }
     scroll_layer_id_when_mouse_over_scrollbar_ = 0;
@@ -2499,8 +2504,9 @@ void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
         std::min(distance_to_scrollbar,
                  DeviceSpaceDistanceToLayer(device_viewport_point, *it));
 
+  // TODO(mithro): Show this be something other then frame time?
   bool should_animate = animation_controller->DidMouseMoveNear(
-      CurrentPhysicalTimeTicks(), distance_to_scrollbar / device_scale_factor_);
+      CurrentFrameTimeTicks(), distance_to_scrollbar / device_scale_factor_);

[danakj, 2014/03/11 18:32:36]

What happens if you get input here and you're not in a BeginImplFrame yet, or
the impl frame takes multiple vsyncs? Is this going to cause any regressions?
+aelias for thoughts on CurrentPhysical -> CurrentFrame time.

   if (should_animate)
     StartScrollbarAnimation();
 }
@@ -2514,7 +2520,7 @@ bool LayerTreeHostImpl::HandleMouseOverScrollbar(LayerImpl* layer_impl,
       scroll_layer_id_when_mouse_over_scrollbar_ = scroll_layer_id;
       bool should_animate =
           layer_impl->scrollbar_animation_controller()->DidMouseMoveNear(
-              CurrentPhysicalTimeTicks(), 0);
+              CurrentFrameTimeTicks(), 0);

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

physical time

       if (should_animate)
         StartScrollbarAnimation();
     } else {
@@ -2830,7 +2836,7 @@ void LayerTreeHostImpl::AnimateScrollbarsRecursive(LayerImpl* layer,
 
 void LayerTreeHostImpl::StartScrollbarAnimation() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::StartScrollbarAnimation");
-  StartScrollbarAnimationRecursive(RootLayer(), CurrentPhysicalTimeTicks());
+  StartScrollbarAnimationRecursive(RootLayer(), CurrentFrameTimeTicks());

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

This is another thing I specifically changed to physical time in
https://chromiumcodereview.appspot.com/16925007

 }
 
 void LayerTreeHostImpl::StartScrollbarAnimationRecursive(LayerImpl* layer,
@@ -2862,23 +2868,16 @@ void LayerTreeHostImpl::SetTreePriority(TreePriority priority) {
   DidModifyTilePriorities();
 }
 
-void LayerTreeHostImpl::ResetCurrentFrameTimeForNextFrame() {
-  current_frame_timeticks_ = base::TimeTicks();
-}
-
-void LayerTreeHostImpl::UpdateCurrentFrameTime(base::TimeTicks* ticks) const {
-  if (ticks->is_null()) {
-    *ticks = CurrentPhysicalTimeTicks();
-  }
-}
-
-base::TimeTicks LayerTreeHostImpl::CurrentFrameTimeTicks() {
-  UpdateCurrentFrameTime(&current_frame_timeticks_);
-  return current_frame_timeticks_;
+void LayerTreeHostImpl::OverrideCurrentFrameTime(base::TimeTicks frame_time) {
+  TRACE_EVENT1("cc",
+               "LayerTreeHostImpl::OverrideCurrentFrameTime",
+               "frame_time",
+               frame_time.ToInternalValue());
+  current_frame_args_.frame_time = frame_time;
 }
 
-base::TimeTicks LayerTreeHostImpl::CurrentPhysicalTimeTicks() const {
-  return gfx::FrameTime::Now();
+base::TimeTicks LayerTreeHostImpl::CurrentFrameTimeTicks() const {
+  return current_frame_args_.frame_time;
 }
 
 scoped_ptr<base::Value> LayerTreeHostImpl::AsValueWithFrame(