Prevent recreation of UI resource holder when created with resource ID

cc/layers/ui_resource_layer.h

 // Copyright 2013 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_UI_RESOURCE_LAYER_H_
 #define CC_LAYERS_UI_RESOURCE_LAYER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/layers/layer.h"
@@ skipping 10 matching lines @@
   static scoped_refptr<UIResourceLayer> Create();
 
   void PushPropertiesTo(LayerImpl* layer) override;
 
   void SetLayerTreeHost(LayerTreeHost* host) override;
 
   void SetBitmap(const SkBitmap& skbitmap);
 
   // An alternative way of setting the resource to allow for sharing.
   void SetUIResourceId(UIResourceId resource_id);
+  // Use this if |resource_id| should be preserved even when LayerTreeHost

[danakj, 2014/11/19 15:56:04]

This doesn't make sense. If you moved it from one LayerTreeHost to another one,
the ID would be completely invalid.

I think that I prefer your previous patch then, with a comment on
SetUIResourceID() that if you use that method you are responsible for updating
the id if the layer moves between compositors.

And can you add a unit test to show that this works as intended?

+  // is changed.
+  void SetPersistentUIResourceId(UIResourceId resource_id);
 
   // Sets a UV transform to be used at draw time. Defaults to (0, 0) and (1, 1).
   void SetUV(const gfx::PointF& top_left, const gfx::PointF& bottom_right);
 
   // Sets an opacity value per vertex. It will be multiplied by the layer
   // opacity value.
   void SetVertexOpacity(float bottom_left,
                         float top_left,
                         float top_right,
                         float bottom_right);
 
   class UIResourceHolder {
    public:
     virtual UIResourceId id() = 0;
     virtual ~UIResourceHolder();
+    virtual bool NeedsRecreation() = 0;
   };
 
  protected:
   UIResourceLayer();
   ~UIResourceLayer() override;
 
   bool HasDrawableContent() const override;
 
   scoped_ptr<UIResourceHolder> ui_resource_holder_;
   SkBitmap bitmap_;
 
   gfx::PointF uv_top_left_;
   gfx::PointF uv_bottom_right_;
   float vertex_opacity_[4];
 
  private:
   scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
   void RecreateUIResourceHolder();
-
-
+  void SetUIResourceIdInternal(UIResourceId resource_id, bool is_persistent);
 
   DISALLOW_COPY_AND_ASSIGN(UIResourceLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_UI_RESOURCE_LAYER_H_