Let the browser know the end of fling

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 2535 matching lines @@
   }
 }
 
 void LayerTreeHostImpl::AnimateTopControls(base::TimeTicks time) {
   if (!top_controls_manager_ || !RootScrollLayer())
     return;
   gfx::Vector2dF scroll = top_controls_manager_->Animate(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,
                                       base::Time wall_clock_time) {
   if (!settings_.accelerated_animation_enabled ||
       animation_registrar_->active_animation_controllers().empty() ||
       !active_tree_->root_layer())
     return;
 
   TRACE_EVENT0("cc", "LayerTreeHostImpl::AnimateLayers");
@@ skipping 339 matching lines @@
   swap_promise_monitor_.erase(monitor);
 }
 
 void LayerTreeHostImpl::NotifySwapPromiseMonitorsOfSetNeedsRedraw() {
   std::set<SwapPromiseMonitor*>::iterator it = swap_promise_monitor_.begin();
   for (; it != swap_promise_monitor_.end(); it++)
     (*it)->OnSetNeedsRedrawOnImpl();
 }
 
 }  // namespace cc