Dispose of MIDIAccessInitializer on contextDestroyed() notification.

Source/modules/webmidi/MIDIAccessInitializer.cpp

 // Copyright 2014 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 "config.h"
 #include "modules/webmidi/MIDIAccessInitializer.h"
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMError.h"
 #include "core/dom/Document.h"
 #include "core/frame/Navigator.h"
 #include "modules/webmidi/MIDIAccess.h"
 #include "modules/webmidi/MIDIController.h"
 #include "modules/webmidi/MIDIOptions.h"
 #include "modules/webmidi/MIDIPort.h"
 
 namespace blink {
 
 MIDIAccessInitializer::MIDIAccessInitializer(ScriptState* scriptState, const MIDIOptions& options)
     : ScriptPromiseResolver(scriptState)
     , m_requestSysex(false)
+    , m_hasBeenDisposed(false)
 {
 #if ENABLE(OILPAN)
     // A prefinalizer has already been registered (as a LifecycleObserver);
     // remove it and register a combined one, as the infrastructure doesn't
     // support multiple prefinalizers for an object.
     //
     // FIXME: Oilpan: remove LifecycleObserver's need for a prefinalizer,
     // and as a consequence, this unregistration step. If the former is independently
     // removed, the unregisterPreFinalizer() call will assert.
     ThreadState::current()->unregisterPreFinalizer(*static_cast<LifecycleObserver*>(this));
     ThreadState::current()->registerPreFinalizer(*this);
 #endif
     if (options.hasSysex())
         m_requestSysex = options.sysex();
 }
 
 MIDIAccessInitializer::~MIDIAccessInitializer()
 {
 #if !ENABLE(OILPAN)
     dispose();
 #endif
 }
 
+void MIDIAccessInitializer::contextDestroyed()
+{
+    dispose();
+}
+
 void MIDIAccessInitializer::dispose()
 {
+    if (m_hasBeenDisposed)
+        return;
+
+    if (!executionContext())
+        return;
+
     // It is safe to cancel a request which is already finished or cancelled.
     Document* document = toDocument(executionContext());
     ASSERT(document);
     if (MIDIController* controller = MIDIController::from(document->frame()))
         controller->cancelSysexPermissionRequest(this);
 
+    m_hasBeenDisposed = true;
+
 #if ENABLE(OILPAN)
     // Delegate to LifecycleObserver's prefinalizer.
     LifecycleObserver::dispose();
 #endif
 }
 
 ScriptPromise MIDIAccessInitializer::start()
 {
     ScriptPromise promise = this->promise();
     m_accessor = MIDIAccessor::create(this);
@@ skipping 60 matching lines @@
 {
     return executionContext()->securityOrigin();
 }
 
 ExecutionContext* MIDIAccessInitializer::executionContext() const
 {
     return scriptState()->executionContext();
 }
 
 } // namespace blink