Re-land: cc: Examine layers to determine if we're ready to activate.

cc/layers/layer_impl.h

 // 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 
@@ skipping 170 matching lines @@
   virtual void DidDraw(ResourceProvider* resource_provider);
 
   virtual ResourceProvider::ResourceId ContentsResourceId() const;
 
   virtual bool HasDelegatedContent() const;
   virtual bool HasContributingDelegatedRenderPasses() const;
   virtual RenderPass::Id FirstContributingRenderPassId() const;
   virtual RenderPass::Id NextContributingRenderPassId(RenderPass::Id id) const;
 
   virtual void UpdateTilePriorities() {}
-  virtual void NotifyTileInitialized(const Tile* tile) {}
+  virtual void NotifyTileStateChanged(const Tile* tile) {}

[enne (OOO), 2014/05/16 21:18:32]

StateChanged is very vague.  What was wrong with Initialized?  What about
ReadyToDraw?  Could you leave a comment here about when this should be called or
what caveats you're worried about?

[reveman, 2014/05/21 22:11:39]

This needs to be called whenever the state of the tile changed in a way that
might cause a visible difference. Examples are:

1. Tile version having been initialized.
2. Higher priority tile version having been initialized.
3. Tile resources freed.
4. Tile marked for on-demand raster.

Initialized or ReadyToDraw doesn't seem right. I added a comment to the client
interface. If you have a better suggestion for name let me know.

 
   virtual ScrollbarLayerImplBase* ToScrollbarLayer();
 
   // Returns true if this layer has content to draw.
   void SetDrawsContent(bool draws_content);
   bool DrawsContent() const { return draws_content_; }
 
   void SetHideLayerAndSubtree(bool hide);
   bool hide_layer_and_subtree() const { return hide_layer_and_subtree_; }
 
@@ skipping 491 matching lines @@
   DrawProperties<LayerImpl> draw_properties_;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> debug_info_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_