Implement HiDPI support in Pepper dev interface

ppapi/proxy/ppb_graphics_2d_proxy.h

 // Copyright (c) 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 PPAPI_PPB_GRAPHICS_2D_PROXY_H_
 #define PPAPI_PPB_GRAPHICS_2D_PROXY_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_completion_callback.h"
 #include "ppapi/c/pp_module.h"
@@ skipping 37 matching lines @@
                                const PP_Point& top_left,
                                bool src_rect_specified,
                                const PP_Rect& src_rect);
   void OnHostMsgScroll(const HostResource& graphics_2d,
                        bool clip_specified,
                        const PP_Rect& clip,
                        const PP_Point& amount);
   void OnHostMsgReplaceContents(const HostResource& graphics_2d,
                                 const HostResource& image_data);
   void OnHostMsgFlush(const HostResource& graphics_2d);
+  void OnHostMsgSetScale(const HostResource& graphics_2d,
+                         float scale);
 
   // Host->plugin message handlers.
   void OnPluginMsgFlushACK(const HostResource& graphics_2d,
                            int32_t pp_error);
 
   // Called in the renderer to send the given flush ACK to the plugin.
   void SendFlushACKToPlugin(int32_t result,
                             const HostResource& graphics_2d);
 
   pp::CompletionCallbackFactory<PPB_Graphics2D_Proxy,
                                 ProxyNonThreadSafeRefCount> callback_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PPB_Graphics2D_Proxy);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PPB_GRAPHICS_2D_PROXY_H_