Unify Android Webview and Chrome's fling

cc/input/layer_scroll_offset_delegate.h

Index: cc/input/layer_scroll_offset_delegate.h
diff --git a/cc/input/layer_scroll_offset_delegate.h b/cc/input/layer_scroll_offset_delegate.h
index 02ba011118dfb5621bf3a53c482b8ae8c1a40e67..ab3d86a4c1ed1229d5616c0a1483ea0dd5550fa5 100644
--- a/cc/input/layer_scroll_offset_delegate.h
+++ b/cc/input/layer_scroll_offset_delegate.h
@@ -6,6 +6,8 @@
 #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"
 
@@ -44,8 +46,14 @@ class LayerScrollOffsetDelegate {
 
   // This is called by the compositor to check whether a delegate-managed fling
   // is active or not.
+  // TODO(jdduke): Remove?

[jdduke (slow), 2015/05/04 22:11:48]

Should we rename this to |IsExternalScrollActive()| (and so on up the chain)?

[hush (inactive), 2015/05/05 21:15:32]

Yes. Will do. I will also remove it when smooth scrolling logic is in chrome.

   virtual bool IsExternalFlingActive() 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() {}