--- a/dom/xbl/nsXBLWindowKeyHandler.cpp
+++ b/dom/xbl/nsXBLWindowKeyHandler.cpp
@@ -528,24 +528,20 @@ nsXBLWindowKeyHandler::HandleEventOnCapt
 
 void
 nsXBLWindowKeyHandler::HandleEventOnCaptureInSystemEventGroup(
                          nsIDOMKeyEvent* aEvent)
 {
   WidgetKeyboardEvent* widgetEvent =
     aEvent->AsEvent()->WidgetEventPtr()->AsKeyboardEvent();
 
-  if (widgetEvent->IsCrossProcessForwardingStopped() ||
-      widgetEvent->mFlags.mOnlySystemGroupDispatchInContent) {
-    return;
-  }
-
-  nsCOMPtr<mozilla::dom::Element> originalTarget =
-    do_QueryInterface(aEvent->AsEvent()->WidgetEventPtr()->mOriginalTarget);
-  if (!EventStateManager::IsRemoteTarget(originalTarget)) {
+  // If the event won't be sent to remote process, this listener needs to do
+  // nothing.
+  if (widgetEvent->mFlags.mOnlySystemGroupDispatchInContent ||
+      !widgetEvent->WillBeSentToRemoteProcess()) {
     return;
   }
 
   if (!HasHandlerForEvent(aEvent)) {
     return;
   }
 
   // If this event wasn't marked as IsCrossProcessForwardingStopped,

--- a/layout/xul/nsMenuBarListener.cpp
+++ b/layout/xul/nsMenuBarListener.cpp
@@ -295,19 +295,27 @@ nsMenuBarListener::KeyPress(nsIDOMEvent*
     }
 
     if (IsAccessKeyPressed(keyEvent) && hasAccessKeyCandidates) {
       // Do shortcut navigation.
       // A letter was pressed. We want to see if a shortcut gets matched. If
       // so, we'll know the menu got activated.
       nsMenuFrame* result = mMenuBarFrame->FindMenuWithShortcut(keyEvent);
       if (result) {
-        // TODO: If the event target is a remote process and not stopped
-        //       sending the event to it, we need to mark the event as
-        //       waiting reply from remote process and stop handling the event.
+        // If the keyboard event matches with a menu item's accesskey and
+        // will be sent to a remote process, it should be executed with
+        // reply event from the focused remote process.  Note that if the
+        // menubar is active, the event is already marked as "stop cross
+        // process dispatching".  So, in that case, this won't wait
+        // reply from the remote content.
+        if (nativeKeyEvent->WillBeSentToRemoteProcess()) {
+          nativeKeyEvent->StopImmediatePropagation();
+          nativeKeyEvent->MarkAsWaitingReplyFromRemoteProcess();
+          return NS_OK;
+        }
         mMenuBarFrame->SetActiveByKeyboard();
         mMenuBarFrame->SetActive(true);
         result->OpenMenu(true);
 
         // The opened menu will listen next keyup event.
         // Therefore, we should clear the keydown flags here.
         mAccessKeyDown = mAccessKeyDownCanceled = false;
 

--- a/widget/BasicEvents.h
+++ b/widget/BasicEvents.h
@@ -784,16 +784,21 @@ public:
    */
   bool HasPluginActivationEventMessage() const;
 
   /**
    * Returns true if the event can be sent to remote process.
    */
   bool CanBeSentToRemoteProcess() const;
   /**
+   * Returns true if the original target is a remote process and the event
+   * will be posted to the remote process later.
+   */
+  bool WillBeSentToRemoteProcess() const;
+  /**
    * Returns true if the event is native event deliverer event for plugin and
    * it should be retarted to focused document.
    */
   bool IsRetargetedNativeEventDelivererForPlugin() const;
   /**
    * Returns true if the event is native event deliverer event for plugin and
    * it should NOT be retarted to focused document.
    */

--- a/widget/WidgetEventImpl.cpp
+++ b/widget/WidgetEventImpl.cpp
@@ -1,22 +1,24 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "gfxPrefs.h"
 #include "mozilla/BasicEvents.h"
 #include "mozilla/ContentEvents.h"
+#include "mozilla/EventStateManager.h"
 #include "mozilla/InternalMutationEvent.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/TextEvents.h"
 #include "mozilla/TouchEvents.h"
+#include "nsIContent.h"
 #include "nsIDOMEventTarget.h"
 #include "nsPrintfCString.h"
 
 namespace mozilla {
 
 /******************************************************************************
  * Global helper methods
  ******************************************************************************/
@@ -345,16 +347,34 @@ WidgetEvent::CanBeSentToRemoteProcess() 
     case eDrop:
       return true;
     default:
       return false;
   }
 }
 
 bool
+WidgetEvent::WillBeSentToRemoteProcess() const
+{
+  // This event won't be posted to remote process if it's already explicitly
+  // stopped.
+  if (IsCrossProcessForwardingStopped()) {
+    return false;
+  }
+
+  // When mOriginalTarget is nullptr, this method shouldn't be used.
+  if (NS_WARN_IF(!mOriginalTarget)) {
+    return false;
+  }
+
+  nsCOMPtr<nsIContent> originalTarget = do_QueryInterface(mOriginalTarget);
+  return EventStateManager::IsRemoteTarget(originalTarget);
+}
+
+bool
 WidgetEvent::IsRetargetedNativeEventDelivererForPlugin() const
 {
   const WidgetPluginEvent* pluginEvent = AsPluginEvent();
   return pluginEvent && pluginEvent->mRetargetToFocusedDocument;
 }
 
 bool
 WidgetEvent::IsNonRetargetedNativeEventDelivererForPlugin() const