Make RenderFrame(Host) own a RenderWidget(Host).

content/common/frame_messages.h

Index: content/common/frame_messages.h
diff --git a/content/common/frame_messages.h b/content/common/frame_messages.h
index fa3159ae2606a400f67140a1f8a52f3c9391f335..84db6946e19379a57c77d36b762d440b23465da7 100644
--- a/content/common/frame_messages.h
+++ b/content/common/frame_messages.h
@@ -195,6 +195,19 @@ IPC_STRUCT_TRAITS_BEGIN(content::CommitNavigationParams)
   IPC_STRUCT_TRAITS_MEMBER(browser_navigation_start)
 IPC_STRUCT_TRAITS_END()
 
+IPC_STRUCT_BEGIN(FrameMsg_NewFrame_WidgetParams)
+  // Gives the routing ID for the RenderWidget that will be attached to the
+  // new RenderFrame. If the RenderFrame does not need a RenderWidget, this
+  // is MSG_ROUTING_NONE and the other parameters are not read.
+  IPC_STRUCT_MEMBER(int, routing_id)
+
+  // Identifier for the output surface for the new RenderWidget.
+  IPC_STRUCT_MEMBER(int, surface_id)
+
+  // Tells the new RenderWidget whether it is initially hidden.
+  IPC_STRUCT_MEMBER(bool, hidden)
+IPC_STRUCT_END()
+
 IPC_STRUCT_BEGIN(FrameMsg_Navigate_Params)
   // TODO(clamy): investigate which parameters are also needed in PlzNavigate
   // and move them to the appropriate NavigationParams struct.
@@ -351,9 +364,10 @@ IPC_MESSAGE_ROUTED0(FrameMsg_DisownOpener)
 // Instructs the renderer to create a new RenderFrame object with |routing_id|.
 // The new frame should be created as a child of the object identified by
 // |parent_routing_id| or as top level if that is MSG_ROUTING_NONE.
-IPC_MESSAGE_CONTROL2(FrameMsg_NewFrame,
+IPC_MESSAGE_CONTROL3(FrameMsg_NewFrame,
                      int /* routing_id */,
-                     int /* parent_routing_id */)
+                     int /* parent_routing_id */,
+                     FrameMsg_NewFrame_WidgetParams /* widget_params */)
 
 // Instructs the renderer to create a new RenderFrameProxy object with
 // |routing_id|. The new proxy should be created as a child of the object