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

cc/input/input_handler.h

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_INPUT_INPUT_HANDLER_H_
 #define CC_INPUT_INPUT_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 110 matching lines @@
   // Similar to ScrollBegin, except the hit test is skipped and scroll always
   // targets at the root layer.
   virtual ScrollStatus RootScrollBegin(ScrollState* scroll_state,
                                        ScrollInputType type) = 0;
 
   // Returns SCROLL_ON_IMPL_THREAD if a layer is actively being scrolled or
   // a subsequent call to ScrollAnimated can begin on the impl thread.
   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
   // scrolls gestures that are direct manipulation (e.g. touch). If there is no
   // room to move the layer in the requested direction, its first ancestor layer
   // that can be scrolled will be moved instead. The return value's |did_scroll|
   // field is set to false if no layer can be moved in the requested direction
   // at all, and set to true if any layer is moved. If the scroll delta hits the
   // root layer, and the layer can no longer move, the root overscroll
   // accumulated within this ScrollBegin() scope is reported in the return
@@ skipping 65 matching lines @@
   InputHandler() {}
   virtual ~InputHandler() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandler);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_INPUT_HANDLER_H_