Make <webview> use out-of-process iframe architecture.

extensions/browser/guest_view/extensions_guest_view_message_filter.h

Index: extensions/browser/guest_view/extensions_guest_view_message_filter.h
diff --git a/extensions/browser/guest_view/extensions_guest_view_message_filter.h b/extensions/browser/guest_view/extensions_guest_view_message_filter.h
index 6e07d415901e40751d8250b2a48c6fbd6851b53b..70678ccb3361eee29cf847a14a93ee920090ea33 100644
--- a/extensions/browser/guest_view/extensions_guest_view_message_filter.h
+++ b/extensions/browser/guest_view/extensions_guest_view_message_filter.h
@@ -22,6 +22,8 @@ class Size;
 
 namespace extensions {
 
+class WebViewGuest;
+
 // This class filters out incoming extensions GuestView-specific IPC messages
 // from thw renderer process. It is created on the UI thread. Messages may be
 // handled on the IO thread or the UI thread.
@@ -43,6 +45,10 @@ class ExtensionsGuestViewMessageFilter : public content::BrowserMessageFilter {
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // Message handlers on the UI thread.
+  void OnAttachToEmbedderFrame(int embedder_local_render_frame_id,
+                               int element_instance_id,
+                               int guest_instance_id,
+                               const base::DictionaryValue& params);
   void OnCanExecuteContentScript(int render_view_id,
                                  int script_id,
                                  bool* allowed);
@@ -61,6 +67,7 @@ class ExtensionsGuestViewMessageFilter : public content::BrowserMessageFilter {
                                            int embedder_render_frame_id,
                                            const gfx::Size& element_size,
                                            content::WebContents* web_contents);
+  void WillAttachCallback(extensions::WebViewGuest* guest);
 
   const int render_process_id_;