Prevent recreation of UI resource holder when created with resource ID

cc/layers/ui_resource_layer.cc

Index: cc/layers/ui_resource_layer.cc
diff --git a/cc/layers/ui_resource_layer.cc b/cc/layers/ui_resource_layer.cc
index 4293b09c5c10d6db58caa28a5b44052cbf9a3bb1..ebb4370b93d6d55d13076379436414b1434575cd 100644
--- a/cc/layers/ui_resource_layer.cc
+++ b/cc/layers/ui_resource_layer.cc
@@ -112,10 +112,16 @@ void UIResourceLayer::SetLayerTreeHost(LayerTreeHost* host) {
 }
 
 void UIResourceLayer::RecreateUIResourceHolder() {
+  UIResourceId ui_resource_id = 0;

[awoloszyn, 2014/10/21 14:29:41]

If someone calls SetBitmap with an empty bitmap, we will destroy the
ScopedUIResourceHolder that contains it but retain its id. This will then be
converted to a SharedUIResourceHolder that is now pointing to a resource_id that
no longer exists. 

I think we need something a bit more explicit rather than trying to infer that
this was a SharedUIResource.

[Changwan Ryu, 2014/10/21 17:28:57]

Good idea. I overlooked it. Done.

+  if (ui_resource_holder_.get())
+    ui_resource_id = ui_resource_holder_->id();
+
   ui_resource_holder_ = nullptr;

[awoloszyn, 2014/10/21 14:29:41]

Something like
// ui_resource_holder_ = nullptr; (remove this)
if (layer_tree_host() && !bitmap_.empty()) {
  //unchanged
} else if (ui_resource_holder_.get() && ui_resource_holder_->NeedsRecreation())
{
  ui_resource_holder_ = nullptr;
}

This was if it was a ScopedUIResource it will get cleaned and if it as a
SharedUIResource, it will get  retained. 

[Changwan Ryu, 2014/10/21 17:28:57]

Done.

   if (layer_tree_host() && !bitmap_.empty()) {
     ui_resource_holder_ =
         ScopedUIResourceHolder::Create(layer_tree_host(), bitmap_);
+  } else if (ui_resource_id != 0) {
+    ui_resource_holder_ = SharedUIResourceHolder::Create(ui_resource_id);
   }
   UpdateDrawsContent(HasDrawableContent());
 }