Bug 1617223 - Remove unused mPostMessageEventQueue from nsGlobalWindowOuter r=bzbarsky

Differential Revision: https://phabricator.services.mozilla.com/D63691

--HG--
extra : moz-landing-system : lando

dom/base/nsGlobalWindowOuter.h

@@ -543,9 +543,6 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> GetTopOuter();
 
   nsresult GetPrompter(nsIPrompt** aPrompt) override;
-
-  RefPtr<mozilla::ThrottledEventQueue> mPostMessageEventQueue;
-
  protected:
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder>
   GetOpenerWindowOuter();