Implement --ozone-platform flag to select OzonePlatform implementation at runtime

ui/base/ozone/platform/test/ozone_platform_test.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_FILE_OZONE_PLATFORM_FILE_H_
 #define UI_OZONE_FILE_OZONE_PLATFORM_FILE_H_
 
 #include "base/files/file_path.h"
 #include "ui/base/ozone/ozone_platform.h"
 #include "ui/events/ozone/evdev/event_factory.h"
 #include "ui/gfx/ozone/impl/file_surface_factory_ozone.h"
 
 namespace ui {
 
 class OzonePlatformTest : public OzonePlatform {
  public:
   OzonePlatformTest(const base::FilePath& dump_file);
   virtual ~OzonePlatformTest();
 
   virtual gfx::SurfaceFactoryOzone* GetSurfaceFactoryOzone() OVERRIDE;
   virtual ui::EventFactoryOzone* GetEventFactoryOzone() OVERRIDE;
 
  private:
   gfx::FileSurfaceFactoryOzone surface_factory_ozone_;
   ui::EventFactoryEvdev event_factory_ozone_;
 
   DISALLOW_COPY_AND_ASSIGN(OzonePlatformTest);
 };
 
+// Constructor hook for use in ozone_platform_list.cc
+OzonePlatform* CreateOzonePlatformTest();
+
 }  // namespace ui
 
 #endif  // UI_OZONE_OZONE_PLATFORM_H_