Let the browser know the end of fling

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 fbc4a820f982496949dce7d3040f3a0518f703c4..587547f8d6b7299468a707ba7c263e7b4c42f1b4 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2553,8 +2553,14 @@ void LayerTreeHostImpl::AnimateTopControls(base::TimeTicks time) {
   UpdateMaxScrollOffset();
   if (RootScrollLayer()->TotalScrollOffset().y() == 0.f)
     return;
-  RootScrollLayer()->ScrollBy(gfx::ScaleVector2d(
-      scroll, 1.f / active_tree_->total_page_scale_factor()));
+  if (scroll.IsZero()) {
+    // This may happen on the first animation step. Force redraw otherwise
+    // the animation would stop because of no new frames.
+    SetNeedsRedraw();
+  } else {
+    RootScrollLayer()->ScrollBy(gfx::ScaleVector2d(
+        scroll, 1.f / active_tree_->total_page_scale_factor()));
+  }
 }
 
 void LayerTreeHostImpl::AnimateLayers(base::TimeTicks monotonic_time,