Create Mojo service for locking/unlocking screen orientation.

content/public/common/screen_orientation.mojom

+// 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.
+
+module content {
+
+enum ScreenOrientationLockType {
+  DEFAULT = 0, // Equivalent to unlock.
+  PORTRAIT_PRIMARY,
+  PORTRAIT_SECONDARY,
+  LANDSCAPE_PRIMARY,
+  LANDSCAPE_SECONDARY,
+  ANY,
+  LANDSCAPE,
+  PORTRAIT,
+  NATURAL,
+};
+
+enum ScreenOrientationLockResult {
+  // The lock was successfully applied.
+  SUCCESS,
+
+  // Failed because locking isn't available on the platform.
+  ERROR_NOT_AVAILABLE,

[qsr, 2014/09/22 13:01:48]

Do we want to remove this, and instead not register a service for platform that
do not support his feature, and then rely on OnConnectionError when requesting
the service?

+ 
+  // Failed because fullscreen is required to lock.
+  ERROR_FULLSCREEN_REQUIRED,
+
+  // Failed because another lock/unlock got called before this one ended.
+  ERROR_CANCELED, 
+};
+
+}