--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -1390,17 +1390,16 @@ nsGlobalWindow::CleanUp(bool aIgnoreModa
     if (asChrome->mMessageManager) {
       static_cast<nsFrameMessageManager*>(
         asChrome->mMessageManager.get())->Disconnect();
     }
   }
 
   mInnerWindowHolder = nullptr;
   mArguments = nullptr;
-  mArgumentsLast = nullptr;
   mArgumentsOrigin = nullptr;
 
   CleanupCachedXBLHandlers(this);
 
   if (mIdleTimer) {
     mIdleTimer->Cancel();
     mIdleTimer = nullptr;
   }
@@ -1619,17 +1618,16 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_
   if (!cb.WantAllTraces() && tmp->IsBlackForCC()) {
     return NS_SUCCESS_INTERRUPTED_TRAVERSE;
   }
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mContext)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mControllers)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArgumentsLast)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPerformance)
 
 #ifdef MOZ_WEBSPEECH
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSpeechSynthesis)
 #endif
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInnerWindowHolder)
@@ -1666,17 +1664,16 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindow)
   nsGlobalWindow::CleanupCachedXBLHandlers(tmp);
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mContext)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mControllers)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mArgumentsLast)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPerformance)
 
 #ifdef MOZ_WEBSPEECH
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSpeechSynthesis)
 #endif
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mInnerWindowHolder)
@@ -2733,17 +2730,16 @@ nsGlobalWindow::DetachFromDocShell()
   ClearControllers();
 
   mChromeEventHandler = nullptr; // force release now
 
   if (mArguments) { 
     // We got no new document after someone called
     // SetArguments(), drop our reference to the arguments.
     mArguments = nullptr;
-    mArgumentsLast = nullptr;
     mArgumentsOrigin = nullptr;
   }
 
   if (mContext) {
     mContext->GC(JS::gcreason::SET_DOC_SHELL);
     mContext = nullptr;
   }
 
@@ -3150,19 +3146,17 @@ nsGlobalWindow::SetArguments(nsIArray *a
 
   // Hold on to the arguments so that we can re-set them once the next
   // document is loaded.
   mArguments = aArguments;
   mArgumentsOrigin = aOrigin;
 
   nsGlobalWindow *currentInner = GetCurrentInnerWindowInternal();
 
-  if (!mIsModalContentWindow) {
-    mArgumentsLast = aArguments;
-  } else if (currentInner) {
+  if (mIsModalContentWindow && currentInner) {
     // SetArguments() is being called on a modal content window that
     // already has an inner window. This can happen when loading
     // javascript: URIs as modal content dialogs. In this case, we'll
     // set up the dialog window, both inner and outer, before we call
     // SetArguments() on the window, so to deal with that, make sure
     // here that the arguments are propagated to the inner window.
 
     currentInner->mArguments = aArguments;

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -1109,17 +1109,16 @@ protected:
   // whether scripts may close the window,
   // even if "dom.allow_scripts_to_close_windows" is false.
   bool                   mAllowScriptsToClose : 1;
 
   nsCOMPtr<nsIScriptContext>    mContext;
   nsWeakPtr                     mOpener;
   nsCOMPtr<nsIControllers>      mControllers;
   nsCOMPtr<nsIArray>            mArguments;
-  nsCOMPtr<nsIArray>            mArgumentsLast;
   nsCOMPtr<nsIPrincipal>        mArgumentsOrigin;
   nsRefPtr<Navigator>           mNavigator;
   nsRefPtr<nsScreen>            mScreen;
   nsRefPtr<nsDOMWindowList>     mFrames;
   nsRefPtr<nsBarProp>           mMenubar;
   nsRefPtr<nsBarProp>           mToolbar;
   nsRefPtr<nsBarProp>           mLocationbar;
   nsRefPtr<nsBarProp>           mPersonalbar;