Support 'extend-to-zoom' viewport descriptor value

Source/core/css/resolver/ViewportStyleResolver.cpp

Index: Source/core/css/resolver/ViewportStyleResolver.cpp
diff --git a/Source/core/css/resolver/ViewportStyleResolver.cpp b/Source/core/css/resolver/ViewportStyleResolver.cpp
index 539cb0e4ab7199d2cbd6381f475980c8cf988c9e..bc6248d9448282a9f978037c19da4ec5b92293e1 100644
--- a/Source/core/css/resolver/ViewportStyleResolver.cpp
+++ b/Source/core/css/resolver/ViewportStyleResolver.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012 Intel Corporation. All rights reserved.
+ * Copyright (C) 2012-2013 Intel Corporation. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -146,6 +146,8 @@ float ViewportStyleResolver::getViewportArgumentValue(CSSPropertyID id) const
         return ViewportArguments::ValuePortrait;
     case CSSValueZoom:
         return defaultValue;
+    case CSSValueExtendToZoom:
+        return ViewportArguments::ValueExtendToZoom;
     case CSSValueFixed:
         return 0;
     default: