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 30ac88d425665f7786501a4e6a7f3f6e0281e8f2..e64878be15224432e829a951c0ad75882c263a7c 100644
--- a/cc/input/input_handler.h
+++ b/cc/input/input_handler.h
@@ -132,6 +132,8 @@ class CC_EXPORT InputHandler {
   virtual ScrollStatus ScrollAnimated(const gfx::Point& viewport_point,
                                       const gfx::Vector2dF& scroll_delta) = 0;
 
+  virtual void AdjustDuration(base::TimeDelta) = 0;

[skobes, 2016/06/08 22:47:28]

I don't think we should ever adjust the duration after the fact. We should just
set it correctly in the first place.

+
   // Scroll the layer selected by |ScrollBegin| by given |scroll_state| delta.
   // Internally, the delta is transformed to local layer's coordinate space for
   // scrolls gestures that are direct manipulation (e.g. touch). If there is no