[Sync] Remove DropAttachments from AttachmentService and SyncData

sync/api/sync_data_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 "sync/api/sync_data.h"
 
 #include <string>
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 99 matching lines @@
                                              AttachmentIdList(),
                                              attachment_service_proxy);
   EXPECT_TRUE(data.IsValid());
   EXPECT_FALSE(data.IsLocal());
   EXPECT_EQ(kId, SyncDataRemote(data).GetId());
   EXPECT_EQ(kLastModifiedTime, SyncDataRemote(data).GetModifiedTime());
   EXPECT_TRUE(data.GetSpecifics().has_preference());
   EXPECT_TRUE(data.GetAttachmentIds().empty());
 }
 
-// TODO(maniscalco): Add test cases that verify GetLocalAttachmentsForUpload and
-// DropAttachments calls are passed through to the underlying AttachmentService.
+// TODO(maniscalco): Add test cases that verify GetLocalAttachmentsForUpload
+// calls are passed through to the underlying AttachmentService.
 
 }  // namespace
 
 }  // namespace syncer