[Sync] Refactor AttachmentStore classes. Introduce concept of referrer.

components/sync_driver/shared_change_processor_unittest.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 "components/sync_driver/shared_change_processor.h"
 
 #include <cstddef>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 33 matching lines @@
   virtual ~SyncSharedChangeProcessorTest() {
     EXPECT_FALSE(db_syncable_service_.get());
   }
 
   virtual base::WeakPtr<syncer::SyncableService> GetSyncableServiceForType(
       syncer::ModelType type) override {
     return db_syncable_service_->AsWeakPtr();
   }
 
   virtual scoped_ptr<syncer::AttachmentService> CreateAttachmentService(
-      const scoped_refptr<syncer::AttachmentStore>& attachment_store,
+      scoped_ptr<syncer::AttachmentStore> attachment_store,
       const syncer::UserShare& user_share,
       const std::string& store_birthday,
       syncer::ModelType model_type,
       syncer::AttachmentService::Delegate* delegate) override {
     return syncer::AttachmentServiceImpl::CreateForTest();
   }
 
  protected:
   virtual void SetUp() override {
     test_user_share_.SetUp();
@@ skipping 122 matching lines @@
 // creates AttachmentService and passes it back to the syncable service.
 TEST_F(SyncSharedChangeProcessorTest, ConnectWithAttachmentStore) {
   SetAttachmentStore();
   Connect();
   EXPECT_TRUE(HasAttachmentService());
 }
 
 }  // namespace
 
 }  // namespace sync_driver