cc: Make animations tick regardless of drawing.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 84c24e056246016c950c3479e58a3d781204ca01..6d60808dbdf894b08e73ff72f6898713271d7783 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -259,6 +259,11 @@ void SingleThreadProxy::Stop() {
   layer_tree_host_ = NULL;
 }
 
+void SingleThreadProxy::OnCanDrawStateChanged(bool can_draw) {
+  DCHECK(Proxy::IsImplThread());
+  layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
+}
+
 void SingleThreadProxy::SetNeedsRedrawOnImplThread() {
   layer_tree_host_->ScheduleComposite();
 }
@@ -395,17 +400,22 @@ bool SingleThreadProxy::DoComposite(
     layer_tree_host_impl_->resource_provider()->
         set_offscreen_context_provider(offscreen_context_provider);
 
-    if (!layer_tree_host_impl_->visible())
+    if (!layer_tree_host_impl_->visible()) {
+      layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
       return false;
+    }
 
-    layer_tree_host_impl_->Animate(base::TimeTicks::Now(), base::Time::Now());
-
-    // We guard prepareToDraw() with canDraw() because it always returns a valid
+    // 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 (!layer_tree_host_impl_->CanDraw())
+    // DrawLayers() depends on the result of PrepareToDraw(), it is guarded on
+    // CanDraw() as well.
+    if (!layer_tree_host_impl_->CanDraw()) {
+      layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
       return false;
+    }
+
+    layer_tree_host_impl_->Animate(base::TimeTicks::Now(), base::Time::Now());
+    layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
 
     LayerTreeHostImpl::FrameData frame;
     layer_tree_host_impl_->PrepareToDraw(&frame);
@@ -413,6 +423,8 @@ bool SingleThreadProxy::DoComposite(
     layer_tree_host_impl_->DidDrawAllLayers(frame);
     output_surface_lost_ = layer_tree_host_impl_->IsContextLost();
 
+    layer_tree_host_impl_->UpdateAnimationState();
+
     layer_tree_host_impl_->BeginNextFrame();
   }