Unify Android Webview and Chrome's fling

android_webview/browser/browser_view_renderer.cc

Index: android_webview/browser/browser_view_renderer.cc
diff --git a/android_webview/browser/browser_view_renderer.cc b/android_webview/browser/browser_view_renderer.cc
index b3fbe01ebf45ff7bc95b4634d2f654afe35fa5c3..2d3748bbc5b594758bdf7962663e4caf8b2c10c1 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -414,6 +414,17 @@ void BrowserViewRenderer::OnDetachedFromWindow() {
   UpdateCompositorIsActive();
 }
 
+void BrowserViewRenderer::OnComputeScroll(base::TimeTicks animation_time) {
+  if (pending_fling_animation_.is_null())
+    return;
+  TRACE_EVENT0("android_webview",
+               "BrowserViewRenderer::FlushPendingScrollAnimation");

[boliu, 2015/06/08 16:54:52]

Fix trace event name

[hush (inactive), 2015/06/09 19:11:33]

Done.

+  DCHECK(!pending_fling_animation_.is_null());
+  AnimationCallback animation = pending_fling_animation_;
+  pending_fling_animation_.Reset();
+  animation.Run(animation_time);
+}
+
 void BrowserViewRenderer::ReleaseHardware() {
   DCHECK(hardware_enabled_);
   ReturnUnusedResource(shared_renderer_state_.PassUncommittedFrameOnUI());
@@ -551,8 +562,8 @@ gfx::Vector2dF BrowserViewRenderer::GetTotalRootLayerScrollOffset() {
   return scroll_offset_dip_;
 }
 
-bool BrowserViewRenderer::IsExternalFlingActive() const {
-  return client_->IsFlingActive();
+bool BrowserViewRenderer::IsExternalScrollActive() const {
+  return client_->IsSmoothScrollingActive();
 }
 
 void BrowserViewRenderer::UpdateRootLayerState(
@@ -606,6 +617,12 @@ BrowserViewRenderer::RootLayerStateAsValue(
   return state;
 }
 
+void BrowserViewRenderer::SetNeedsAnimateScroll(
+    const AnimationCallback& scroll_animation) {
+  pending_fling_animation_ = scroll_animation;
+  PostInvalidateWithFallback();

[boliu, 2015/06/08 16:54:52]

Actually I'm eating my words. You said it's ok if compositor is not ticked. Also
fallback tick doesn't call computeScroll either. In that case, just call
client->PostInvalidate for now, and add a note why fallback tick is not needed.

We are close to removing the fallback tick altogether soon, so don't want to add
any more dependencies on it. Sounds like it's not necessary here anyway.

[hush (inactive), 2015/06/09 19:11:33]

Okay. I will just postInvalidate and add a comment there.

+}
+
 void BrowserViewRenderer::DidOverscroll(gfx::Vector2dF accumulated_overscroll,
                                         gfx::Vector2dF latest_overscroll_delta,
                                         gfx::Vector2dF current_fling_velocity) {
@@ -618,7 +635,10 @@ void BrowserViewRenderer::DidOverscroll(gfx::Vector2dF accumulated_overscroll,
       scaled_overscroll_delta + overscroll_rounding_error_);
   overscroll_rounding_error_ =
       scaled_overscroll_delta - rounded_overscroll_delta;
-  client_->DidOverscroll(rounded_overscroll_delta);
+  gfx::Vector2dF fling_velocity_pixels =
+      gfx::ScaleVector2d(current_fling_velocity, physical_pixel_scale);
+
+  client_->DidOverscroll(rounded_overscroll_delta, fling_velocity_pixels);
 }
 
 void BrowserViewRenderer::PostInvalidate() {
@@ -641,7 +661,8 @@ void BrowserViewRenderer::PostInvalidateWithFallback() {
   bool throttle_fallback_tick =
       (is_paused_ && !clear_view_) || (attached_to_window_ && !window_visible_);
 
-  if (throttle_fallback_tick || fallback_tick_pending_)
+  if (throttle_fallback_tick || fallback_tick_pending_ ||
+      !pending_fling_animation_.is_null())

[boliu, 2015/06/08 16:54:52]

don't forget to remove this

(Seems to be backwards anyway. The idea is cc *wants* fallback ticks if there is
a pending animation, in case the real draw doesn't come back.)

[hush (inactive), 2015/06/09 19:11:33]

okay,.. removed this. And yes. The logic here is backward :/

     return;
 
   DCHECK(post_fallback_tick_.IsCancelled());