Portals: Move ForwardMessageToPortalHost to an associated interface

This is a follow up to https://crrev.com/c/1423462.

Moving ForwardMessageToPortalHost to FrameNavigationControl associates
it with the Frame navigation messages and the legacy Frame IPC channel,
ensuring a defined ordering between postMessage and navigation messages.

Bug: 914120
Change-Id: I1fdb9a5be5b2d034764d28464aaeba955efc9320
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1536536Reviewed-by: Lucas Gadani <lfg@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Adithya Srinivasan <adithyas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644386}

content/browser/frame_host/render_frame_host_impl.cc

@@ -1069,7 +1069,8 @@ void RenderFrameHostImpl::ForwardMessageToPortalHost(
     if (target_origin != GetLastCommittedOrigin())
       return;
   }
-  frame_->ForwardMessageToPortalHost(message, source_origin, target_origin);
+  GetNavigationControl()->ForwardMessageToPortalHost(message, source_origin,
+                                                     target_origin);
 }
 
 SiteInstanceImpl* RenderFrameHostImpl::GetSiteInstance() {

content/common/frame.mojom

@@ -59,11 +59,6 @@ interface Frame {
   // Cancels blocked requests. BlockRequests must have been called before.
   CancelBlockedRequests();
 
-  // Forwards message to the portal's main frame.
-  ForwardMessageToPortalHost(string message,
-                             url.mojom.Origin source_origin,
-                             url.mojom.Origin? target_origin);
-
   // Set the lifecycle state.
   SetLifecycleState(blink.mojom.FrameLifecycleState state);
 
@@ -221,6 +216,11 @@ interface FrameNavigationControl {
                    mojo_base.mojom.String16 target_origin,
                    blink.mojom.TransferableMessage message);
 
+  // Forwards message to the portal's main frame.
+  ForwardMessageToPortalHost(string message,
+                             url.mojom.Origin source_origin,
+                             url.mojom.Origin? target_origin);
+
   // Called on the main frame of a page embedded in a Portal when it is
   // activated. The frame has the option to adopt the previous page as a portal
   // identified by |portal_token| with the interface |portal|. The activation