cc: Avoid updating animations in the background without an active tree

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 "base/basictypes.h"
 #include "base/containers/hash_tables.h"
@@ skipping 110 matching lines @@
     bool start_ready_animations = true;
     layer_tree_host_impl_->UpdateAnimationState(start_ready_animations);
     layer_tree_host_impl_->ResetCurrentFrameTimeForNextFrame();
   }
 
   void SetActive(bool active) {
     if (active != time_source_->Active())
       time_source_->SetActive(active);
   }
 
+  bool Active() const {
+    return time_source_->Active();
+  }
+
  private:
   LayerTreeHostImplTimeSourceAdapter(
       LayerTreeHostImpl* layer_tree_host_impl,
       scoped_refptr<DelayBasedTimeSource> time_source)
       : layer_tree_host_impl_(layer_tree_host_impl),
         time_source_(time_source) {
     time_source_->SetClient(this);
   }
 
   LayerTreeHostImpl* layer_tree_host_impl_;
@@ skipping 108 matching lines @@
     pending_tree()->ApplyScrollDeltasSinceBeginFrame();
     pending_tree_->set_needs_update_draw_properties();
     pending_tree_->UpdateDrawProperties();
     // Start working on newly created tiles immediately if needed.
     if (!tile_manager_ || !manage_tiles_needed_)
       NotifyReadyToActivate();
     else
       ManageTiles();
   } else {
     active_tree_->set_needs_update_draw_properties();
+    if (time_source_client_adapter_ && time_source_client_adapter_->Active())
+      DCHECK(active_tree_->root_layer());
   }
 
   client_->SendManagedMemoryStats();
 }
 
 bool LayerTreeHostImpl::CanDraw() const {
   // Note: If you are changing this function or any other function that might
   // affect the result of CanDraw, make sure to call
   // client_->OnCanDrawStateChanged in the proper places and update the
   // NotifyIfCanDrawChanged test.
@@ skipping 549 matching lines @@
 }
 
 void LayerTreeHostImpl::MainThreadHasStoppedFlinging() {
   if (input_handler_client_)
     input_handler_client_->MainThreadHasStoppedFlinging();
 }
 
 void LayerTreeHostImpl::UpdateBackgroundAnimateTicking(
     bool should_background_tick) {
   DCHECK(proxy_->IsImplThread());
+  if (should_background_tick)
+    DCHECK(active_tree_->root_layer());
 
   bool enabled = should_background_tick &&
                  !animation_registrar_->active_animation_controllers().empty();
 
   // Lazily create the time_source adapter so that we can vary the interval for
   // testing.
   if (!time_source_client_adapter_) {
     time_source_client_adapter_ = LayerTreeHostImplTimeSourceAdapter::Create(
         this,
         DelayBasedTimeSource::Create(
@@ skipping 658 matching lines @@
     const RenderingStats& stats =
         rendering_stats_instrumentation_->GetRenderingStats();
     paint_time_counter_->SavePaintTime(
         stats.main_stats.paint_time + stats.main_stats.record_time +
             stats.impl_stats.rasterize_time_for_now_bins_on_pending_tree);
   }
 
   client_->DidActivatePendingTree();
   if (!tree_activation_callback_.is_null())
     tree_activation_callback_.Run();
+
+  if (time_source_client_adapter_ && time_source_client_adapter_->Active())
+    DCHECK(active_tree_->root_layer());
 }
 
 void LayerTreeHostImpl::SetVisible(bool visible) {
   DCHECK(proxy_->IsImplThread());
 
   if (visible_ == visible)
     return;
   visible_ = visible;
   DidVisibilityChange(this, visible_);
   EnforceManagedMemoryPolicy(ActualManagedMemoryPolicy());
@@ skipping 1052 matching lines @@
 
 ResourceProvider::ResourceId LayerTreeHostImpl::ResourceIdForUIResource(
     UIResourceId uid) const {
   UIResourceMap::const_iterator iter = ui_resource_map_.find(uid);
   if (iter != ui_resource_map_.end())
     return iter->second;
   return 0;
 }
 
 }  // namespace cc