Unify Android Webview and Chrome's fling

android_webview/browser/browser_view_renderer.h

Index: android_webview/browser/browser_view_renderer.h
diff --git a/android_webview/browser/browser_view_renderer.h b/android_webview/browser/browser_view_renderer.h
index 477a039cecc344617fb77a5424e38c8310d498e0..e6365e761efcf46b874aada5949d872a3fdb9795 100644
--- a/android_webview/browser/browser_view_renderer.h
+++ b/android_webview/browser/browser_view_renderer.h
@@ -74,6 +74,7 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient {
   void OnSizeChanged(int width, int height);
   void OnAttachedToWindow(int width, int height);
   void OnDetachedFromWindow();
+  void OnComputeScroll(base::TimeTicks animation_time);
 
   // Sets the scale for logical<->physical pixel conversions.
   void SetDipScale(float dip_scale);
@@ -106,7 +107,8 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient {
                             float page_scale_factor,
                             float min_page_scale_factor,
                             float max_page_scale_factor) override;
-  bool IsExternalFlingActive() const override;
+  bool IsExternalScrollActive() const override;
+  void SetNeedsAnimateFling(const AnimationCallback& fling_animation) override;

[jdduke (slow), 2015/05/18 21:18:34]

Let's go ahead and rename this to |SetNeedsAnimateScroll|, |scroll_animation|
and also below |FlushPendingScrollAnimation|.

[hush (inactive), 2015/05/19 18:14:59]

Done.

   void DidOverscroll(gfx::Vector2dF accumulated_overscroll,
                      gfx::Vector2dF latest_overscroll_delta,
                      gfx::Vector2dF current_fling_velocity) override;
@@ -144,6 +146,10 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient {
   // compositor that are not directly exposed here.
   void ForceFakeCompositeSW();
 
+  // Honor the requested fling animation as contained in
+  // |pending_fling_animation_|.
+  void FlushPendingFlingAnimation(base::TimeTicks animation_time);
+
   gfx::Vector2d max_scroll_offset() const;
 
   void UpdateMemoryPolicy();
@@ -179,6 +185,11 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient {
 
   gfx::Size size_;
 
+  // Used to drive a fling animation as requested by the compositor. This acts
+  // as a  single-shot animation; the compositor will continually post an
+  // animation callback as long as they're required.
+  AnimationCallback pending_fling_animation_;
+
   // Current scroll offset in CSS pixels.
   gfx::Vector2dF scroll_offset_dip_;