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 333bb288faacbf9562472e815fa729165823721f..d98bbec120a987446791e11f9f9dd23f1db7cb3e 100644
--- a/extensions/browser/guest_view/extensions_guest_view_message_filter.h
+++ b/extensions/browser/guest_view/extensions_guest_view_message_filter.h
@@ -27,6 +27,8 @@ class GuestViewManager;
 
 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.
@@ -49,6 +51,10 @@ class ExtensionsGuestViewMessageFilter
   guest_view::GuestViewManager* GetOrCreateGuestViewManager() 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);
@@ -66,6 +72,7 @@ class ExtensionsGuestViewMessageFilter
                                            int embedder_render_frame_id,
                                            const gfx::Size& element_size,
                                            content::WebContents* web_contents);
+  void WillAttachCallback(extensions::WebViewGuest* guest);
 
   static const uint32 kFilteredMessageClasses[];