Simple Cache: restore the high-res timer

net/disk_cache/simple/simple_util.h

Index: net/disk_cache/simple/simple_util.h
diff --git a/net/disk_cache/simple/simple_util.h b/net/disk_cache/simple/simple_util.h
index 3bb80b9540238393aa859a9791e6a4faab7d458f..ef518695813cff891658644aa2a831da35c3b1a8 100644
--- a/net/disk_cache/simple/simple_util.h
+++ b/net/disk_cache/simple/simple_util.h
@@ -63,8 +63,8 @@ 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