drive: FileCache::Store marks the entry as dirty if empty MD5 is given

chrome/browser/chromeos/drive/file_cache.h

 // Copyright (c) 2012 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_FILE_CACHE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_CACHE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 70 matching lines @@
   // false.
   bool FreeDiskSpaceIfNeededFor(int64 num_bytes);
 
   // Checks if file corresponding to |id| exists in cache, and returns
   // FILE_ERROR_OK with |cache_file_path| storing the path to the file.
   // |cache_file_path| must not be null.
   FileError GetFile(const std::string& id, base::FilePath* cache_file_path);
 
   // Stores |source_path| as a cache of the remote content of the file
   // with |id| and |md5|.
+  // Pass an empty string as MD5 to mark the entry as dirty.
   FileError Store(const std::string& id,
                   const std::string& md5,
                   const base::FilePath& source_path,
                   FileOperationType file_operation_type);
 
   // Pins the specified entry.
   FileError Pin(const std::string& id);
 
   // Unpins the specified entry.
   FileError Unpin(const std::string& id);
@@ skipping 91 matching lines @@
   // invalidate its weak pointers before any other members are destroyed.
   // This object should be accessed only on |blocking_task_runner_|.
   base::WeakPtrFactory<FileCache> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(FileCache);
 };
 
 }  // namespace internal
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_CACHE_H_