Screen Orientation API: cleanup, simplify and fix implementation.

public/platform/WebScreenOrientationType.h

+// 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.
+
+#ifndef WebScreenOrientationType_h
+#define WebScreenOrientationType_h
+
+namespace blink {
+
+enum WebScreenOrientationType {
+    WebScreenOrientationPortraitPrimary = 1,
+    WebScreenOrientationPortraitSecondary,
+    WebScreenOrientationLandscapePrimary,
+    WebScreenOrientationLandscapeSecondary
+};
+
+} // namespace blink
+
+#endif // WebScreenOrientationType_h