Harmonize LayerTreeHost/LayerTreeHostImpl synchronization steps

cc/trees/layer_tree_impl.h

 // Copyright 2012 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.
 
 #ifndef CC_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 113 matching lines @@
   const RenderSurfaceImpl* RootRenderSurface() const;
   bool LayerListIsEmpty() const;
   void SetRootLayerForTesting(std::unique_ptr<LayerImpl>);
   void OnCanDrawStateChangedForTree();
   bool IsRootLayer(const LayerImpl* layer) const;
   std::unique_ptr<OwnedLayerImplList> DetachLayers();
 
   void SetPropertyTrees(PropertyTrees* property_trees);
   PropertyTrees* property_trees() { return &property_trees_; }
 
+#if DCHECK_IS_ON()
+  // Returns true if the layer tree properties are safe to access. This occurs
+  // when the layer tree host is not currently syncing properties, or when a
+  // sync is in process but the property tree has been updated. See:
+  // |LayerTreeHostImpl::SyncState|.
+  bool PropertyTreeSyncComplete() const {
+    return layer_tree_host_impl_->SyncStateComplete(SYNCED_PROPERTY_TREES);

[enne (OOO), 2017/05/12 17:25:06]

Is it possible to just have this hidden inside of the property_trees()
LayerTreeImpl::property_trees accessor?

[pdr., 2017/05/15 18:30:24]

I've added a TODO comment here that we want to do this.

+  }
+#endif
+
+  void PushPropertyTreesTo(LayerTreeImpl* tree_impl);
   void PushPropertiesTo(LayerTreeImpl* tree_impl);
 
   void MoveChangeTrackingToLayers();
 
   void ForceRecalculateRasterScales();
 
   LayerImplList::const_iterator begin() const;
   LayerImplList::const_iterator end() const;
   LayerImplList::reverse_iterator rbegin();
   LayerImplList::reverse_iterator rend();
@@ skipping 440 matching lines @@
 
   std::unique_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_