Reset the (Local|Remote)Frame receiver on detach.

We don't want to receive messages after we are detached so ensure
we reset the receiver on detach.

BUG=1020551

Change-Id: Iddc8a8a9e1e8f9e998845c876e544c0b770cdfe6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894918
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711834}

third_party/blink/renderer/core/frame/local_frame.cc

@@ -368,6 +368,7 @@ void LocalFrame::DetachImpl(FrameDetachType type) {
 
   supplements_.clear();
   frame_scheduler_.reset();
+  receiver_.reset();
   WeakIdentifierMap<LocalFrame>::NotifyObjectDestroyed(this);
 }
 

third_party/blink/renderer/core/frame/remote_frame.cc

@@ -160,6 +160,7 @@ void RemoteFrame::DetachImpl(FrameDetachType type) {
   To<RemoteDOMWindow>(dom_window_.Get())->FrameDetached();
   if (cc_layer_)
     SetCcLayer(nullptr, false, false);
+  receiver_.reset();
 }
 
 bool RemoteFrame::DetachDocument() {