Add missing #include around sequenced_worker_pool.h in //chrome

chrome/browser/extensions/updater/local_extension_cache.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_UPDATER_LOCAL_EXTENSION_CACHE_H_
 #define CHROME_BROWSER_EXTENSIONS_UPDATER_LOCAL_EXTENSION_CACHE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 
+namespace base {
+class SequencedTaskRunner;
+}
+
 namespace extensions {
 
 // Cache .crx files in some local dir for future use. Cache keeps only latest
 // version of the extensions. Only one instance of LocalExtensionCache can work
 // with the same directory. But LocalExtensionCache instance can be shared
 // between multiple clients. Public interface can be used only from UI thread.
 class LocalExtensionCache {
  public:
   // Callback invoked on UI thread when PutExtension is completed.
   typedef base::Callback<void(const base::FilePath& file_path,
@@ skipping 240 matching lines @@
 
   // Weak factory for callbacks from the backend and delayed tasks.
   base::WeakPtrFactory<LocalExtensionCache> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalExtensionCache);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_UPDATER_LOCAL_EXTENSION_CACHE_H_