Prevent recreation of UI resource holder when created with resource ID

cc/layers/ui_resource_layer.h

Index: cc/layers/ui_resource_layer.h
diff --git a/cc/layers/ui_resource_layer.h b/cc/layers/ui_resource_layer.h
index 3bfd9b2f109d1d0e995060d4d63141f21772d96b..2e0ae2b47f8f7d311e1edf8f4944a783e532ad63 100644
--- a/cc/layers/ui_resource_layer.h
+++ b/cc/layers/ui_resource_layer.h
@@ -28,6 +28,9 @@ class CC_EXPORT UIResourceLayer : public Layer {
 
   // 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);
@@ -43,6 +46,7 @@ class CC_EXPORT UIResourceLayer : public Layer {
    public:
     virtual UIResourceId id() = 0;
     virtual ~UIResourceHolder();
+    virtual bool NeedsRecreation() = 0;
   };
 
  protected:
@@ -61,8 +65,7 @@ class CC_EXPORT UIResourceLayer : public Layer {
  private:
   scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
   void RecreateUIResourceHolder();
-
-
+  void SetUIResourceIdInternal(UIResourceId resource_id, bool is_persistent);
 
   DISALLOW_COPY_AND_ASSIGN(UIResourceLayer);
 };