[screen-orientation] Update implementation to match recent spec changes.

Source/modules/screen_orientation/PartialScreenOrientation.idl

Index: Source/modules/screen_orientation/PartialScreenOrientation.idl
diff --git a/Source/modules/screen_orientation/PartialScreenOrientation.idl b/Source/modules/screen_orientation/PartialScreenOrientation.idl
new file mode 100644
index 0000000000000000000000000000000000000000..2905343b8eb2fe3ae71e86e6da27057d495929a7
--- /dev/null
+++ b/Source/modules/screen_orientation/PartialScreenOrientation.idl
@@ -0,0 +1,9 @@
+// Copyright 2014 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.
+
+[
+    RuntimeEnabled=ScreenOrientation
+] partial interface Screen {
+    [CallWith=ScriptState] readonly attribute ScreenOrientation orientation;
+};