Promptly finalize CacheStorage's embedder object.

Source/modules/cachestorage/CacheStorage.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/cachestorage/CacheStorage.h"
 
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "core/dom/DOMException.h"
@@ skipping 251 matching lines @@
     const ScriptPromise promise = resolver->promise();
 
     if (m_webCacheStorage)
         m_webCacheStorage->dispatchMatch(new MatchCallbacks(resolver), webRequest, Cache::toWebQueryParams(options));
     else
         resolver->reject(createNoImplementationException());
 
     return promise;
 }
 
-DEFINE_TRACE(CacheStorage)
-{
-    visitor->trace(m_nameToCacheMap);
-}
-
 CacheStorage::CacheStorage(WeakPtr<GlobalFetch::ScopedFetcher> fetcher, PassOwnPtr<WebServiceWorkerCacheStorage> webCacheStorage)
     : m_scopedFetcher(fetcher)
     , m_webCacheStorage(webCacheStorage)
 {
 }
 
+CacheStorage::~CacheStorage()
+{
+}
+
+void CacheStorage::dispose()
+{
+    m_webCacheStorage.clear();
+}
+
+DEFINE_TRACE(CacheStorage)
+{
+    visitor->trace(m_nameToCacheMap);
+}
+
 } // namespace blink