[SyncFS] Support Delete operation on LevelDBWrapper::Iterator

chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.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_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_
 
 #include <map>
 #include <string>
 
@@ skipping 38 matching lines @@
   class Iterator {
    public:
     explicit Iterator(LevelDBWrapper* db);
     ~Iterator();
 
     bool Valid();
     void Seek(const std::string& target);
     void SeekToFirst();
     void SeekToLast();
     void Next();
+    void Delete();
     leveldb::Slice key();
     leveldb::Slice value();
 
    private:
     // Advances internal iterators to be valid.
     void AdvanceIterators();
 
     LevelDBWrapper* db_;  // do not own
     scoped_ptr<leveldb::Iterator> db_iterator_;
     PendingOperationMap::iterator map_iterator_;
@@ skipping 29 matching lines @@
 
   PendingOperationMap pending_;
 
   DISALLOW_COPY_AND_ASSIGN(LevelDBWrapper);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_