cc: Make animations tick regardless of drawing.

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index a09850a5ece8968e1f7868140f1c74fe0202676a..5879fc6911103bb5381babe2892473348ec23e2f 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -348,6 +348,7 @@ void ThreadProxy::OnCanDrawStateChanged(bool can_draw) {
   TRACE_EVENT1(
       "cc", "ThreadProxy::OnCanDrawStateChanged", "can_draw", can_draw);
   scheduler_on_impl_thread_->SetCanDraw(can_draw);
+  layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
 }
 
 void ThreadProxy::OnHasPendingTreeStateChanged(bool has_pending_tree) {
@@ -811,6 +812,8 @@ void ThreadProxy::ScheduledActionCommit() {
   layer_tree_host_->FinishCommitOnImplThread(layer_tree_host_impl_.get());
   layer_tree_host_impl_->CommitComplete();
 
+  layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
+
   next_frame_is_newly_committed_frame_on_impl_thread_ = true;
 
   if (layer_tree_host_->settings().impl_side_painting &&
@@ -876,6 +879,7 @@ ThreadProxy::ScheduledActionDrawAndSwapInternal(bool forced_draw) {
 
   layer_tree_host_impl_->ActivatePendingTreeIfNeeded();
   layer_tree_host_impl_->Animate(monotonic_time, wall_clock_time);
+  layer_tree_host_impl_->UpdateBackgroundAnimateTicking();
 
   // This method is called on a forced draw, regardless of whether we are able
   // to produce a frame, as the calling site on main thread is blocked until its
@@ -900,6 +904,8 @@ ThreadProxy::ScheduledActionDrawAndSwapInternal(bool forced_draw) {
   }
   layer_tree_host_impl_->DidDrawAllLayers(frame);
 
+  layer_tree_host_impl_->UpdateAnimationState();

[ajuma, 2013/04/04 15:28:47]

If the call to PrepareToDraw (above) returned false, causing us to skip the
frame, we don't want to start animations (to avoid regressing
http://crbug.com/123593), but it makes sense to continue ticking/finishing
in-progress animations. We could add a |DoNotPromoteAnimations| argument to
UpdateAnimationState, passing it on to LayerAnimationController::UpdateState,
preventing this from calling PromoteStartedAnimations.

[danakj, 2013/04/04 18:28:25]

Ok, I've done this and added
LayerTreeHostAnimationTestCheckerboardDoesntStartAnimations.RunMultiThread.

This test does not run in single thread mode as it does not  skip drawing due to
checkerboard.

+
   // Check for tree activation.
   if (completion_event_for_commit_held_on_tree_activation_ &&
       !layer_tree_host_impl_->pending_tree()) {