Add FileSystemMountPointProvider::CreateFileReader() which returns appropriate Reader instance

webkit/fileapi/sandbox_mount_point_provider.h

Index: webkit/fileapi/sandbox_mount_point_provider.h
diff --git a/webkit/fileapi/sandbox_mount_point_provider.h b/webkit/fileapi/sandbox_mount_point_provider.h
index 9bdddc036bfedc7f16d6b15e411775222728fc14..c92cda22c0fcae5158249206661d2f36b9b7ae45 100644
--- a/webkit/fileapi/sandbox_mount_point_provider.h
+++ b/webkit/fileapi/sandbox_mount_point_provider.h
@@ -93,6 +93,11 @@ class SandboxMountPointProvider
       const FilePath& virtual_path,
       base::MessageLoopProxy* file_proxy,
       FileSystemContext* context) const OVERRIDE;
+  virtual webkit_blob::FileReader* CreateFileReader(
+    const GURL& url,
+    int64 offset,
+    base::MessageLoopProxy* file_proxy,
+    FileSystemContext* context) const OVERRIDE;
 
   FilePath old_base_path() const;
   FilePath new_base_path() const;