Add IPC plumbing code for FileSystem API's openFileSystem

chrome/browser/renderer_host/resource_message_filter.h

Index: chrome/browser/renderer_host/resource_message_filter.h
diff --git a/chrome/browser/renderer_host/resource_message_filter.h b/chrome/browser/renderer_host/resource_message_filter.h
index 6f47917c03d5a67ad22c95591b0d65d1221cdcaa..83d498537b69835b8beaffd9c39b6bc0f38e4fe8 100644
--- a/chrome/browser/renderer_host/resource_message_filter.h
+++ b/chrome/browser/renderer_host/resource_message_filter.h
@@ -35,6 +35,7 @@ class AudioRendererHost;
 class ChromeURLRequestContext;
 class DatabaseDispatcherHost;
 class DOMStorageDispatcherHost;
+class FileSystemDispatcherHost;
 struct FontDescriptor;
 class GeolocationDispatcherHost;
 class HostZoomMap;
@@ -472,6 +473,9 @@ class ResourceMessageFilter : public IPC::ChannelProxy::MessageFilter,
   scoped_refptr<device_orientation::DispatcherHost>
       device_orientation_dispatcher_host_;
 
+  // Handles FileSystem API related messages
+  scoped_refptr<FileSystemDispatcherHost> file_system_dispatcher_host_;
+
   DISALLOW_COPY_AND_ASSIGN(ResourceMessageFilter);
 };