Add support for 'display-mode' MQ defined in Manifest spec

Source/core/css/DisplayModeProperties.h

Index: Source/core/css/DisplayModeProperties.h
diff --git a/Source/core/css/DisplayModeProperties.h b/Source/core/css/DisplayModeProperties.h
new file mode 100644
index 0000000000000000000000000000000000000000..17ac305e37163796063c0112fd61fdbb3747bd66
--- /dev/null
+++ b/Source/core/css/DisplayModeProperties.h
@@ -0,0 +1,20 @@
+// Copyright 2015 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 DisplayModeProperties_h
+#define DisplayModeProperties_h
+
+namespace blink {
+
+enum DisplayMode {
+    DisplayModeUndefined, // User for override setting (ie. not set).
+    DisplayModeBrowser,
+    DisplayModeMinimalUi,
+    DisplayModeStandalone,
+    DisplayModeFullscreen
+};
+
+}
+
+#endif