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

Source/core/css/MediaValues.cpp

Index: Source/core/css/MediaValues.cpp
diff --git a/Source/core/css/MediaValues.cpp b/Source/core/css/MediaValues.cpp
index 18bb3e41b8c4d809715e2a5fbc58e64b8fd0f8a2..2776089bf747ab02695d003aa18c7beb7956bdcc 100644
--- a/Source/core/css/MediaValues.cpp
+++ b/Source/core/css/MediaValues.cpp
@@ -105,6 +105,17 @@ const String MediaValues::calculateMediaType(LocalFrame* frame) const
     return frame->view()->mediaType();
 }
 
+DisplayMode MediaValues::calculateDisplayMode(LocalFrame* frame) const
+{
+    ASSERT(frame);
+    DisplayMode mode = frame->host()->settings().displayModeOverride();
+
+    if (mode != DisplayModeUndefined)
+        return mode;
+
+    return DisplayModeBrowser;
+}
+
 bool MediaValues::calculateThreeDEnabled(LocalFrame* frame) const
 {
     ASSERT(frame && frame->contentRenderer() && frame->contentRenderer()->compositor());