Take MT jank into account when animating the scroll offset on CC

cc/input/input_handler.h

Index: cc/input/input_handler.h
diff --git a/cc/input/input_handler.h b/cc/input/input_handler.h
index bd11a620bbff2038ab1a8e74a38abf5f56c39eee..8d0f0c49982fc87b4f3b8c784c3a3f98320eda78 100644
--- a/cc/input/input_handler.h
+++ b/cc/input/input_handler.h
@@ -128,8 +128,12 @@ class CC_EXPORT InputHandler {
   virtual ScrollStatus ScrollAnimatedBegin(
       const gfx::Point& viewport_point) = 0;
 
+  // Returns SCROLL_ON_IMPL_THREAD if an animation is initiated on the impl
+  // thread. delayed_by is the delay that is taken into account when determining
+  // the duration of the animation.

[tdresser, 2016/08/25 15:55:54]

More importantly, it determines the start time of the animation, correct?

[ymalik, 2016/08/29 14:52:05]

Not quite, since the animation will still start at the same time that it would
have without this delay. It just finishes faster because the duration of the
animation is adjusted by "delayed_by". Does that make sense?

   virtual ScrollStatus ScrollAnimated(const gfx::Point& viewport_point,
-                                      const gfx::Vector2dF& scroll_delta) = 0;
+                                      const gfx::Vector2dF& scroll_delta,
+                                      base::TimeDelta delayed_by) = 0;
 
   // Scroll the layer selected by |ScrollBegin| by given |scroll_state| delta.
   // Internally, the delta is transformed to local layer's coordinate space for