Move Cache Storage API implementation to modules/cachestorage

Source/modules/cachestorage/GlobalCacheStorage.h

 // Copyright 2015 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.
 
 #ifndef GlobalCacheStorage_h
 #define GlobalCacheStorage_h
 
 namespace blink {
 
 class CacheStorage;
 class DOMWindow;
 class ExceptionState;
 class WorkerGlobalScope;
 
 class GlobalCacheStorage {
 public:
     static CacheStorage* caches(DOMWindow&, ExceptionState&);
     static CacheStorage* caches(WorkerGlobalScope&, ExceptionState&);
 };
 
 } // namespace blink
 
 #endif // GlobalCacheStorage_h