Simple Cache: restore the high-res timer

net/disk_cache/simple/simple_util.h

 // Copyright (c) 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 NET_DISK_CACHE_SIMPLE_SIMPLE_UTIL_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_UTIL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 45 matching lines @@
 // returns the number of bytes in the file.
 NET_EXPORT_PRIVATE int64 GetFileSizeFromKeyAndDataSize(const std::string& key,
                                                        int32 data_size);
 
 // Given the key to an entry, and an offset into a stream on that entry, returns
 // the file offset corresponding to |data_offset|.
 NET_EXPORT_PRIVATE int64 GetFileOffsetFromKeyAndDataOffset(
     const std::string& key,
     int data_offset);
 
-// Fills |out_time| with the time the file last modified time.
-// TODO(gavinp): Remove this function.
+// Fills |out_time| with the time the file last modified time. Unlike the
+// functions in platform_file.h, the time resolution is milliseconds.
 NET_EXPORT_PRIVATE bool GetMTime(const base::FilePath& path,
                                  base::Time* out_mtime);
 }  // namespace simple_backend
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_UTIL_H_