Prevent recreation of UI resource holder when created with resource ID

cc/layers/ui_resource_layer.cc

 // 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.
 
 #include "cc/layers/ui_resource_layer.h"
 
 #include "cc/layers/ui_resource_layer_impl.h"
 #include "cc/resources/prioritized_resource.h"
 #include "cc/resources/resource_update.h"
 #include "cc/resources/resource_update_queue.h"
@@ skipping 94 matching lines @@
   if (host == layer_tree_host())
     return;
 
   Layer::SetLayerTreeHost(host);
 
   // Recreate the resource hold against the new LTH.
   RecreateUIResourceHolder();
 }
 
 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());
 }
 
 void UIResourceLayer::SetBitmap(const SkBitmap& skbitmap) {
   bitmap_ = skbitmap;
 
   RecreateUIResourceHolder();
   SetNeedsCommit();
 }
@@ skipping 28 matching lines @@
     gfx::Size image_size =
         layer_tree_host()->GetUIResourceSize(ui_resource_holder_->id());
     layer_impl->SetUIResourceId(ui_resource_holder_->id());
     layer_impl->SetImageBounds(image_size);
     layer_impl->SetUV(uv_top_left_, uv_bottom_right_);
     layer_impl->SetVertexOpacity(vertex_opacity_);
   }
 }
 
 }  // namespace cc