zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

ui/ozone/public/surface_factory_ozone.h

 // Copyright (c) 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 UI_OZONE_PUBLIC_SURFACE_FACTORY_OZONE_H_
 #define UI_OZONE_PUBLIC_SURFACE_FACTORY_OZONE_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/native_library.h"
@@ skipping 60 matching lines @@
   enum BufferUsage {
     MAP,
     SCANOUT,
   };
 
   typedef void* (*GLGetProcAddressProc)(const char* name);
   typedef base::Callback<void(base::NativeLibrary)> AddGLLibraryCallback;
   typedef base::Callback<void(GLGetProcAddressProc)>
       SetGLGetProcAddressProcCallback;
 
-  SurfaceFactoryOzone();
   virtual ~SurfaceFactoryOzone();
 
   // Returns the singleton instance.
   static SurfaceFactoryOzone* GetInstance();
 
   // Returns native platform display handle. This is used to obtain the EGL
   // display connection for the native display.
   virtual intptr_t GetNativeDisplay();
 
   // Returns Drm file descriptor. This is used to obtain access to the
@@ skipping 34 matching lines @@
   // caller. desired_list contains list of desired EGL properties and values.
   virtual const int32* GetEGLSurfaceProperties(const int32* desired_list);
 
   // Get the hal struct to check for overlay support.
   virtual OverlayCandidatesOzone* GetOverlayCandidates(
       gfx::AcceleratedWidget w);
 
   // Create a single native buffer to be used for overlay planes or zero copy
   // for |widget| representing a particular display controller or default
   // display controller for kNullAcceleratedWidget.
+  // It can be called on any thread.
   virtual scoped_refptr<NativePixmap> CreateNativePixmap(
       gfx::AcceleratedWidget widget,
       gfx::Size size,
       BufferFormat format,
       BufferUsage usage);
 
   // Sets the overlay plane to switch to at the next page flip.
   // |w| specifies the screen to display this overlay plane on.
   // |plane_z_order| specifies the stacking order of the plane relative to the
   // main framebuffer located at index 0.
@@ skipping 13 matching lines @@
 
   // Returns true if overlays can be shown at z-index 0, replacing the main
   // surface. Combined with surfaceless extensions, it allows for an
   // overlay-only mode.
   virtual bool CanShowPrimaryPlaneAsOverlay();
 
   // Returns true if the platform is able to create buffers for a specific usage
   // such as MAP for zero copy or SCANOUT for display controller.
   virtual bool CanCreateNativePixmap(BufferUsage usage);
 
+ protected:
+  SurfaceFactoryOzone();
+
  private:
-  static SurfaceFactoryOzone* impl_;  // not owned
+  DISALLOW_COPY_AND_ASSIGN(SurfaceFactoryOzone);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PUBLIC_SURFACE_FACTORY_OZONE_H_