Update screen.orientation to follow the latest version of the specs.

LayoutTests/fast/dom/Window/resources/window-property-collector.js

 function collectProperties()
 {
     // Collect properties of the top-level window, since touching the properties
     // of a DOMWindow affects its internal C++ state.
     collectPropertiesHelper(window, []);
 
     propertiesToVerify.sort(function (a, b)
     {
         if (a.property < b.property)
             return -1
@@ skipping 42 matching lines @@
     case "navigator.appCodeName":
     case "navigator.appName":
     case "navigator.language":
     case "navigator.onLine":
     case "navigator.platform":
     case "navigator.product":
     case "navigator.productSub":
     case "navigator.vendor":
         expected = "window." + propertyPath;
         break;
+    case "screen.orientation":
+        expected = "'portrait-primary'";
+        break;
     }
 
     insertExpectedResult(path, expected);
 }
 
 function collectPropertiesHelper(object, path)
 {
     if (path.length > 20)
         throw 'Error: probably looping';
 
@@ skipping 23 matching lines @@
         } else if (type == "string") {
             emitExpectedResult(path, "''");
         } else if (type == "number") {
             emitExpectedResult(path, "0");
         } else if (type == "boolean") {
             emitExpectedResult(path, "false");
         }
         path.pop();
     }
 }