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

cc/trees/single_thread_proxy.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/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "cc/output/context_provider.h"
 #include "cc/output/output_surface.h"
@@ skipping 82 matching lines @@
 void SingleThreadProxy::SetLayerTreeHostClientReady() {
   // Scheduling is controlled by the embedder in the single thread case, so
   // nothing to do.
 }
 
 void SingleThreadProxy::SetVisible(bool visible) {
   DebugScopedSetImplThread impl(this);
   layer_tree_host_impl_->SetVisible(visible);
 
   // Changing visibility could change ShouldComposite().
-  layer_tree_host_impl_->UpdateBackgroundAnimateTicking(!ShouldComposite());
+  UpdateBackgroundAnimateTicking();
 }
 
 void SingleThreadProxy::CreateAndInitializeOutputSurface() {
   TRACE_EVENT0(
       "cc", "SingleThreadProxy::CreateAndInitializeOutputSurface");
   DCHECK(Proxy::IsMainThread());
 
   scoped_ptr<OutputSurface> output_surface = first_output_surface_.Pass();
   if (!output_surface)
     output_surface = layer_tree_host_->CreateOutputSurface();
@@ skipping 144 matching lines @@
 
     layer_tree_host_->DeleteContentsTexturesOnImplThread(
         layer_tree_host_impl_->resource_provider());
     layer_tree_host_impl_.reset();
   }
   layer_tree_host_ = NULL;
 }
 
 void SingleThreadProxy::OnCanDrawStateChanged(bool can_draw) {
   DCHECK(Proxy::IsImplThread());
-  layer_tree_host_impl_->UpdateBackgroundAnimateTicking(!ShouldComposite());
+  UpdateBackgroundAnimateTicking();
 }
 
 void SingleThreadProxy::NotifyReadyToActivate() {
   // Thread-only feature.
   NOTREACHED();
 }
 
 void SingleThreadProxy::SetNeedsRedrawOnImplThread() {
   layer_tree_host_->ScheduleComposite();
 }
@@ skipping 141 matching lines @@
   layer_tree_host_->DidBeginFrame();
   return result;
 }
 
 bool SingleThreadProxy::ShouldComposite() const {
   DCHECK(Proxy::IsImplThread());
   return layer_tree_host_impl_->visible() &&
          layer_tree_host_impl_->CanDraw();
 }
 
+void SingleThreadProxy::UpdateBackgroundAnimateTicking() {
+  DCHECK(Proxy::IsImplThread());
+  layer_tree_host_impl_->UpdateBackgroundAnimateTicking(
+         !ShouldComposite() &&
+         layer_tree_host_impl_->active_tree()->root_layer());
+}
+
 bool SingleThreadProxy::DoComposite(
     scoped_refptr<cc::ContextProvider> offscreen_context_provider,
     base::TimeTicks frame_begin_time,
     gfx::Rect device_viewport_damage_rect,
     bool for_readback,
     LayerTreeHostImpl::FrameData* frame) {
   DCHECK(!layer_tree_host_->output_surface_lost());
 
   bool lost_output_surface = false;
   {
     DebugScopedSetImplThread impl(this);
     base::AutoReset<bool> mark_inside(&inside_draw_, true);
 
     layer_tree_host_impl_->SetOffscreenContextProvider(
         offscreen_context_provider);
 
     bool can_do_readback = layer_tree_host_impl_->renderer()->CanReadPixels();
 
     // We guard PrepareToDraw() with CanDraw() because it always returns a valid
     // frame, so can only be used when such a frame is possible. Since
     // DrawLayers() depends on the result of PrepareToDraw(), it is guarded on
     // CanDraw() as well.
     if (!ShouldComposite() || (for_readback && !can_do_readback)) {
-      layer_tree_host_impl_->UpdateBackgroundAnimateTicking(true);
+      UpdateBackgroundAnimateTicking();

[brianderson, 2013/08/29 01:03:09]

For the same reasons as in ThreadProxy, I do not always enable or disable
background ticking in the DoComposite method.

       return false;
     }
 
     layer_tree_host_impl_->Animate(
         layer_tree_host_impl_->CurrentFrameTimeTicks(),
         layer_tree_host_impl_->CurrentFrameTime());
-    layer_tree_host_impl_->UpdateBackgroundAnimateTicking(false);
+    UpdateBackgroundAnimateTicking();
 
     layer_tree_host_impl_->PrepareToDraw(frame, device_viewport_damage_rect);
     layer_tree_host_impl_->DrawLayers(frame, frame_begin_time);
     layer_tree_host_impl_->DidDrawAllLayers(*frame);
     lost_output_surface = layer_tree_host_impl_->IsContextLost();
 
     bool start_ready_animations = true;
     layer_tree_host_impl_->UpdateAnimationState(start_ready_animations);
 
     layer_tree_host_impl_->ResetCurrentFrameTimeForNextFrame();
@@ skipping 14 matching lines @@
 void SingleThreadProxy::DidSwapFrame() {
   if (next_frame_is_newly_committed_frame_) {
     next_frame_is_newly_committed_frame_ = false;
     layer_tree_host_->DidCommitAndDrawFrame();
   }
 }
 
 bool SingleThreadProxy::CommitPendingForTesting() { return false; }
 
 }  // namespace cc