NOT FOR LANDING - [WebView] Allow fling animation via the LayerScrollOffsetDelegate

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index f394d52494ea5750809c128277c1f25afb07d363..f2efc54af1e5f4df2420fe32d3a40a65bc15a83e 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -399,8 +399,7 @@ bool LayerTreeHostImpl::CanDraw() const {
 }
 
 void LayerTreeHostImpl::Animate(base::TimeTicks monotonic_time) {
-  if (input_handler_client_)
-    input_handler_client_->Animate(monotonic_time);
+  AnimateFling(monotonic_time);

[mkosiba (inactive), 2014/05/15 13:48:51]

I don't think we want to call this at all if layer_scroll_offset_delegate is not
null

[jdduke (slow), 2014/05/15 14:15:43]

Oops yeah that's definitely what I had planned.

   AnimatePageScale(monotonic_time);
   AnimateLayers(monotonic_time);
   AnimateScrollbars(monotonic_time);
@@ -471,6 +470,19 @@ void LayerTreeHostImpl::StartPageScaleAnimation(
   client_->RenewTreePriority();
 }
 
+void LayerTreeHostImpl::SetNeedsAnimateFling() {
+  if (root_layer_scroll_offset_delegate_ &&
+      (CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
+       CurrentlyScrollingLayer() == OuterViewportScrollLayer())) {
+    // Hacky callback approach...
+    root_layer_scroll_offset_delegate_->SetNeedsAnimate(
+        base::Bind(&LayerTreeHostImpl::AnimateFling, AsWeakPtr()));
+    return;
+  }
+
+  SetNeedsAnimate();
+}
+
 bool LayerTreeHostImpl::IsCurrentlyScrollingLayerAt(
     const gfx::Point& viewport_point,
     InputHandler::ScrollInputType type) {
@@ -2758,6 +2770,12 @@ void LayerTreeHostImpl::ScrollViewportBy(gfx::Vector2dF scroll_delta) {
     InnerViewportScrollLayer()->ScrollBy(unused_delta);
 }
 
+void LayerTreeHostImpl::AnimateFling(base::TimeTicks monotonic_time) {
+  DCHECK(proxy_->IsImplThread());
+  if (input_handler_client_)
+    input_handler_client_->AnimateFling(monotonic_time);
+}
+
 void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks monotonic_time) {
   if (!page_scale_animation_)
     return;