chromeos: Use WriteBatch to update DriveResourceMetadata DB

chrome/browser/chromeos/drive/drive_resource_metadata_storage.h

 // Copyright 2013 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_CHROMEOS_DRIVE_DRIVE_RESOURCE_METADATA_STORAGE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_RESOURCE_METADATA_STORAGE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 27 matching lines @@
   // Initializes this object.
   bool Initialize();
 
   // Sets the largest changestamp.
   void SetLargestChangestamp(int64 largest_changestamp);
 
   // Gets the largest changestamp.
   int64 GetLargestChangestamp();
 
   // Puts the entry to this storage.
-  void PutEntry(const DriveEntryProto& entry);
+  bool PutEntry(const DriveEntryProto& entry);
 
   // Returns an entry stored in this storage.
   scoped_ptr<DriveEntryProto> GetEntry(const std::string& resource_id);
 
   // Removes an entry from this storage.
-  void RemoveEntry(const std::string& resource_id);
+  bool RemoveEntry(const std::string& resource_id);
 
   // Iterates over entries stored in this storage.
   void Iterate(const IterateCallback& callback);
 
-  // Puts child under the parent.
-  void PutChild(const std::string& parent_resource_id,
-                const std::string& child_name,
-                const std::string& child_resource_id);
-
   // Returns resource ID of the parent's child.
   std::string GetChild(const std::string& parent_resource_id,
                        const std::string& child_name);
 
   // Returns resource IDs of the parent's children.
   void GetChildren(const std::string& parent_resource_id,
                    std::vector<std::string>* children);
 
-  // Removes child from the parent.
-  void RemoveChild(const std::string& parent_resource_id,
-                   const std::string& child_name);
-
  private:
   friend class DriveResourceMetadataStorageTest;
 
+  // Returns a string to be used as a key for child entry.
+  static std::string GetChildEntryKey(const std::string& parent_resource_id,
+                                      const std::string& child_name);
+
   // Puts header.
   void PutHeader(const DriveResourceMetadataHeader& header);
 
   // Gets header.
   scoped_ptr<DriveResourceMetadataHeader> GetHeader();
 
   // Checks validity of the data.
   bool CheckValidity();
 
   // Path to the directory where the data is stored.
   base::FilePath directory_path_;
 
   // Entries stored in this storage.
   scoped_ptr<leveldb::DB> resource_map_;
 
   DISALLOW_COPY_AND_ASSIGN(DriveResourceMetadataStorage);
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_RESOURCE_METADATA_STORAGE_H_