Implement the file chooser as a new resource "host"

ppapi/proxy/plugin_dispatcher.h

Index: ppapi/proxy/plugin_dispatcher.h
diff --git a/ppapi/proxy/plugin_dispatcher.h b/ppapi/proxy/plugin_dispatcher.h
index 5022f6994c99974b4c086f6dcff195504fb10b7b..b952b156f0c5161ba9b7c89d62379dc2b7138cf7 100644
--- a/ppapi/proxy/plugin_dispatcher.h
+++ b/ppapi/proxy/plugin_dispatcher.h
@@ -32,6 +32,8 @@ class ResourceCreationAPI;
 
 namespace proxy {
 
+class ResourceMessageReplyParams;
+
 // Used to keep track of per-instance data.
 struct InstanceData {
   InstanceData();
@@ -140,6 +142,9 @@ class PPAPI_PROXY_EXPORT PluginDispatcher
   void ForceFreeAllInstances();
 
   // IPC message handlers.
+  void OnMsgResourceReply(
+      const ppapi::proxy::ResourceMessageReplyParams& reply_params,
+      const IPC::Message& nested_msg);
   void OnMsgSupportsInterface(const std::string& interface_name, bool* result);
   void OnMsgSetPreferences(const Preferences& prefs);