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..0afc4db89e333975c91ff57495f6811a70c18c57 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"
 
@@ -44,7 +46,14 @@ class LayerScrollOffsetDelegate {
 
   // This is called by the compositor to check whether a delegate-managed fling
   // is active or not.
-  virtual bool IsExternalFlingActive() const = 0;
+  // TODO(hush): Remove after WebView's smooth scrolling path is unified with
+  // Chrome's.
+  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() {}