fileapi: Add modification time check for FileSystemFileStreamReader

webkit/fileapi/file_system_mount_point_provider.h

Index: webkit/fileapi/file_system_mount_point_provider.h
diff --git a/webkit/fileapi/file_system_mount_point_provider.h b/webkit/fileapi/file_system_mount_point_provider.h
index c36a602e81c182f55e242899d807c295300acd33..876ce40c135e00590e6ab8a65db3abf2c2d96273 100644
--- a/webkit/fileapi/file_system_mount_point_provider.h
+++ b/webkit/fileapi/file_system_mount_point_provider.h
@@ -87,13 +87,18 @@ class FILEAPI_EXPORT FileSystemMountPointProvider {
       base::PlatformFileError* error_code) const = 0;
 
   // Creates a new file stream reader for a given filesystem URL |url| with an
-  // offset |offset|.
+  // offset |offset|. |expected_modification_time| specifies the expected last
+  // modification if the value is non-null, the reader will check the underlying
+  // file's actual modification time to see if the file has been modified, and
+  // if it does any succeeding read operations should fail with
+  // ERR_UPLOAD_FILE_CHANGED error.
   // The returned object must be owned and managed by the caller.
   // This method itself does *not* check if the given path exists and is a
   // regular file.
   virtual webkit_blob::FileStreamReader* CreateFileStreamReader(
     const FileSystemURL& url,
     int64 offset,
+    const base::Time& expected_modification_time,
     FileSystemContext* context) const = 0;
 
   // Creates a new file stream writer for a given filesystem URL |url| with an