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

extensions/renderer/guest_view/guest_view_request.h

Index: extensions/renderer/guest_view/guest_view_request.h
diff --git a/extensions/renderer/guest_view/guest_view_request.h b/extensions/renderer/guest_view/guest_view_request.h
index dbb7343d01e9085c284aa447fa8a8a5048609ebc..a7538e0c8950ecb6d64daf57f0b772094c0ce24b 100644
--- a/extensions/renderer/guest_view/guest_view_request.h
+++ b/extensions/renderer/guest_view/guest_view_request.h
@@ -92,6 +92,21 @@ class GuestViewDetachRequest : public GuestViewRequest {
   DISALLOW_COPY_AND_ASSIGN(GuestViewDetachRequest);
 };
 
+class GuestViewAttachIframeRequest : public GuestViewRequest {
+ public:
+  GuestViewAttachIframeRequest(GuestViewContainer* container,
+                               int guest_instance_id,
+                               v8::Local<v8::Function> callback,
+                               v8::Isolate* isolate);
+  ~GuestViewAttachIframeRequest() override;
+
+  void PerformRequest() override;
+  void HandleResponse(const IPC::Message& message) override;
+
+ private:
+  const int guest_instance_id_;
+};
+
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_GUEST_VIEW_EXTENSIONS_GUEST_VIEW_CONTAINER_H_