[Extensions] Pull ExtensionId into its own file

extensions/browser/api/storage/local_value_store_cache.cc

 // 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 "extensions/browser/api/storage/local_value_store_cache.h"
 
 #include <stddef.h>
 
 #include <limits>
 
 #include "content/public/browser/browser_thread.h"
 #include "extensions/browser/api/storage/weak_unlimited_settings_storage.h"
 #include "extensions/browser/value_store/value_store_factory.h"
 #include "extensions/common/api/storage.h"
+#include "extensions/common/extension.h"
 #include "extensions/common/permissions/permissions_data.h"
 
 using content::BrowserThread;
 
 namespace extensions {
 
 namespace {
 
 // Returns the quota limit for local storage, taken from the schema in
 // extensions/common/api/storage.json.
@@ skipping 57 matching lines @@
       settings_namespace::LOCAL, model_type, extension->id());
   linked_ptr<SettingsStorageQuotaEnforcer> storage(
       new SettingsStorageQuotaEnforcer(quota_, std::move(store)));
   DCHECK(storage.get());
 
   storage_map_[extension->id()] = storage;
   return storage.get();
 }
 
 }  // namespace extensions