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

components/guest_view/common/guest_view_messages.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // IPC messages for GuestViews.
 // Multiply-included message file, hence no include guard.
 
 #include "base/values.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START GuestViewMsgStart
 
 // Messages sent from the browser to the renderer.
 
+// Tells the embedder that a guest has been attached in --site-per-process mode.
+IPC_MESSAGE_CONTROL1(GuestViewMsg_AttachToEmbedderFrame_ACK,
+                     int /* element_instance_id */)
+
 // Once a RenderView proxy has been created for the guest in the embedder render
 // process, this IPC informs the embedder of the proxy's routing ID.
 IPC_MESSAGE_CONTROL2(GuestViewMsg_GuestAttached,
                      int /* element_instance_id */,
                      int /* source_routing_id */)
 
 // This IPC tells the browser process to detach the provided
 // |element_instance_id| from a GuestViewBase if it is attached to one.
 // In other words, routing of input and graphics will no longer flow through
 // the container associated with the provided ID.
 IPC_MESSAGE_CONTROL1(GuestViewMsg_GuestDetached,
                      int /* element_instance_id*/)
 
 // Messages sent from the renderer to the browser.
 
 // Sent by the renderer to set initialization parameters of a Browser Plugin
 // that is identified by |element_instance_id|.
 IPC_MESSAGE_CONTROL3(GuestViewHostMsg_AttachGuest,
                      int /* element_instance_id */,
                      int /* guest_instance_id */,
                      base::DictionaryValue /* attach_params */)
 
+// We have a RenderFrame with routing id of |embedder_local_frame_routing_id|.
+// We want this local frame to be replaced with a remote frame that points
+// to a <webview>. This message will attach the local frame to the <webview>

[Fady Samuel, 2015/06/23 14:33:00]

nit: avoid references to <webview>.

[lazyboy, 2015/06/23 23:00:00]

Done.

+// guest. The <webview> is identified by its ID: |guest_instance_id|.
+IPC_MESSAGE_CONTROL4(GuestViewHostMsg_AttachToEmbedderFrame,
+                     int /* embedder_local_frame_routing_id */,
+                     int /* element_instance_id */,
+                     int /* guest_instance_id */,
+                     base::DictionaryValue /* params */)
+
 // Sent by the renderer when a GuestView (identified by |view_instance_id|) has
 // been created in JavaScript.
 IPC_MESSAGE_CONTROL2(GuestViewHostMsg_ViewCreated,
                      int /* view_instance_id */,
                      std::string /* view_type */)
 
 // Sent by the renderer when a GuestView (identified by |view_instance_id|) has
 // been garbage collected in JavaScript.
 IPC_MESSAGE_CONTROL1(GuestViewHostMsg_ViewGarbageCollected,
                      int /* view_instance_id */)