Making scheduler run ANIMATE after a COMMIT (instead of LayerTreeHostImpl).

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 318 matching lines @@
 void LayerTreeHostImpl::BeginCommit() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::BeginCommit");
 
   if (UsePendingTreeForSync())
     CreatePendingTree();
 }
 
 void LayerTreeHostImpl::CommitComplete() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::CommitComplete");
 
+  // Ask to be animated if there are animations

[mithro-old, 2014/10/15 07:18:19]

These lines appear to be the cause of the hang issue in
https://code.google.com/p/chromium/issues/detail?id=421931. I'm still trying to
figure out the exact cause though.

[Sami, 2014/10/20 09:44:04]

Sorry for missing this in the review :( This is weird since I'd think the *lack*
of calls to SetNeedsAnimate would cause hangs. I suspect the reason is related
to how we signal the beginning and end of animations to JS somehow. I ran into a
similar but opposite issue when originally splitting animating and drawing:
https://codereview.chromium.org/206793003/

[brianderson, 2014/10/20 18:05:05]

These lines really shouldn't have caused us to hang. It is likely that it's only
causing us to hit an existing bug more often.

We should try to fix ToT so it can work with these lines in and then see if it
fixes the other hangs we are seeing in earlier versions of Chrome.

+  if (needs_animate_layers())
+    SetNeedsAnimate();
+
   if (pending_tree_)
     pending_tree_->ApplyScrollDeltasSinceBeginMainFrame();
   sync_tree()->set_needs_update_draw_properties();
 
   if (settings_.impl_side_painting) {
     // Impl-side painting needs an update immediately post-commit to have the
     // opportunity to create tilings.  Other paths can call UpdateDrawProperties
     // more lazily when needed prior to drawing.
     sync_tree()->UpdateDrawProperties();
     // Start working on newly created tiles immediately if needed.
@@ skipping 3022 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc