WindowAudioWorklet: gracefully handle detached use.

third_party/WebKit/Source/modules/webaudio/WindowAudioWorklet.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/webaudio/WindowAudioWorklet.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "modules/webaudio/AudioWorklet.h"
@@ skipping 11 matching lines @@
   WindowAudioWorklet* supplement = static_cast<WindowAudioWorklet*>(
       Supplement<LocalDOMWindow>::from(window, supplementName()));
   if (!supplement) {
     supplement = new WindowAudioWorklet(window);
     provideTo(window, supplementName(), supplement);
   }
   return *supplement;
 }
 
 Worklet* WindowAudioWorklet::audioWorklet(DOMWindow& window) {
+  if (!window.frame())
+    return nullptr;
   return from(toLocalDOMWindow(window)).audioWorklet(toLocalDOMWindow(window));
 }
 
 AudioWorklet* WindowAudioWorklet::audioWorklet(LocalDOMWindow& window) {
   if (!m_audioWorklet && getExecutionContext()) {
     DCHECK(window.frame());
     m_audioWorklet = AudioWorklet::create(window.frame());
   }
   return m_audioWorklet.get();
 }
@@ skipping 11 matching lines @@
   m_audioWorklet = nullptr;
 }
 
 DEFINE_TRACE(WindowAudioWorklet) {
   visitor->trace(m_audioWorklet);
   Supplement<LocalDOMWindow>::trace(visitor);
   ContextLifecycleObserver::trace(visitor);
 }
 
 }  // namespace blink