Unify Android Webview and Chrome's fling

cc/input/layer_scroll_offset_delegate.h

 // Copyright 2013 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_LAYER_SCROLL_OFFSET_DELEGATE_H_
 #define CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
 
 #include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/time/time.h"
 #include "ui/gfx/geometry/scroll_offset.h"
 #include "ui/gfx/geometry/size_f.h"
 
 namespace cc {
 
 // The LayerScrollOffsetDelegate allows for the embedder to take ownership of
 // the scroll offset of the root layer.
 //
 // The LayerScrollOffsetDelegate is only used on the impl thread.
 class LayerScrollOffsetDelegate {
@@ skipping 18 matching lines @@
   virtual void UpdateRootLayerState(
       const gfx::ScrollOffset& total_scroll_offset,
       const gfx::ScrollOffset& max_scroll_offset,
       const gfx::SizeF& scrollable_size,
       float page_scale_factor,
       float min_page_scale_factor,
       float max_page_scale_factor) = 0;
 
   // This is called by the compositor to check whether a delegate-managed fling
   // is active or not.
-  virtual bool IsExternalFlingActive() const = 0;
+  // TODO(jdduke): Remove?

[aelias_OOO_until_Jul13, 2015/05/09 03:32:05]

Seems we can't yet because of the other smooth scrolls, is that right?

[hush (inactive), 2015/05/12 19:08:45]

Right. We will still need to keep it until we can unify smooth scrolls with
Chrome. I will upload a followup CL after this CL is submitted.
Jared and I had a very brief discussion about how to unify smooth scrolls a
while back.
The high level plan for that is we will introduce 2 new gesture events on
ContentViewCore(maybe call them SmoothScrollStart/Cancel), do the plumbing up
until web_gesture_curve_impl.cc to expose Scroller::startScroll.

+  virtual bool IsExternalScrollActive() const = 0;
+
+  // This is called by the compositor when a fling hitting the root layer
+  // requires a scheduled animation update.
+  typedef base::Callback<void(base::TimeTicks)> AnimationCallback;
+  virtual void SetNeedsAnimate(const AnimationCallback& animation) = 0;
 
  protected:
   LayerScrollOffsetDelegate() {}
   virtual ~LayerScrollOffsetDelegate() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_