Remove implicit conversions from scoped_refptr to T* in cc/trees/

cc/trees/layer_tree_impl.h

 // Copyright 2012 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_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <list>
 #include <string>
 #include <vector>
@@ skipping 55 matching lines @@
   }
   virtual ~LayerTreeImpl();
 
   void Shutdown();
   void ReleaseResources();
 
   // Methods called by the layer tree that pass-through or access LTHI.
   // ---------------------------------------------------------------------------
   const LayerTreeSettings& settings() const;
   const RendererCapabilitiesImpl& GetRendererCapabilities() const;
-  ContextProvider* context_provider() const;
+  scoped_refptr<ContextProvider> context_provider() const;

[danakj, 2014/08/25 20:25:01]

I don't think we want to add references to this thing freely. What code is
requiring this?

[dcheng, 2014/08/25 20:56:58]

This is the logic to try to catch temporary scoped_refptrs being returned
kicking in again.

Foo* foo() { return ReturnsScopedRefPtr(); } would be potentially unsafe.

But I've reverted this as well and just changed the implementation to call
.get().

   OutputSurface* output_surface() const;
   ResourceProvider* resource_provider() const;
   TileManager* tile_manager() const;
   FrameRateCounter* frame_rate_counter() const;
   PaintTimeCounter* paint_time_counter() const;
   MemoryHistory* memory_history() const;
   bool resourceless_software_draw() const;
   gfx::Size device_viewport_size() const;
   bool IsActiveTree() const;
   bool IsPendingTree() const;
@@ skipping 264 matching lines @@
 
   int render_surface_layer_list_id_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_