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

extensions/common/guest_view/extensions_guest_view_messages.h

Index: extensions/common/guest_view/extensions_guest_view_messages.h
diff --git a/extensions/common/guest_view/extensions_guest_view_messages.h b/extensions/common/guest_view/extensions_guest_view_messages.h
index 61da7fcec0a364082c954e0ef21e607d6a9afe70..9d05188ef07ae8c24607c8eaa775e441b28fa67b 100644
--- a/extensions/common/guest_view/extensions_guest_view_messages.h
+++ b/extensions/common/guest_view/extensions_guest_view_messages.h
@@ -23,8 +23,21 @@ IPC_MESSAGE_CONTROL1(ExtensionsGuestViewMsg_CreateMimeHandlerViewGuestACK,
 IPC_MESSAGE_CONTROL1(ExtensionsGuestViewMsg_MimeHandlerViewGuestOnLoadCompleted,
                      int /* element_instance_id */)
 
+// Tells a <webview> that its contentWindow is ready to be exposed.
+IPC_MESSAGE_CONTROL1(ExtensionsGuestViewMsg_ContentWindowReady,
+                     int /* element_instance_id */)
+
 // Messages sent from the renderer to the browser.
 
+// 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>
+// guest. The <webview> is identified by its ID: |guest_instance_id|.
+IPC_MESSAGE_CONTROL3(ExtensionsGuestViewHostMsg_AttachToEmbedderFrame,
+                     int /* embedder_local_frame_routing_id */,
+                     int /* element_instance_id */,
+                     int /* guest_instance_id */)
+
 // Queries whether the RenderView of the provided |routing_id| is allowed to
 // inject the script with the provided |script_id|.
 IPC_SYNC_MESSAGE_CONTROL2_1(