Use Promises for screen.lockOrientation().

LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html

Index: LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html
diff --git a/LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html b/LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html
index cc931a49fb8f982d2799fc4e92b20161486be216..7ba8d37c56b37a9a63cf07c9bcc5fa55dae8d346 100644
--- a/LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html
+++ b/LayoutTests/screen_orientation/resources/sandboxed-iframe-locking.html
@@ -1,9 +1,14 @@
 <script>
-    var exceptionName = "";
-    try {
-        screen.lockOrientation("portrait-primary");
-    } catch (ex) {
-        exceptionName = ex.name;
-    }
-    parent.window.postMessage(exceptionName, "*");
+    var msg = "";
+    screen.lockOrientation("portrait-primary").then(function() {
+    }, function(error) {
+        msg = error.name;
+    });
+
+    // FIXME: for the moment, tests gets notified when there is a failure but
+    // not a success, this hack should allow us to still have the test running.
+    // That should be removed as soon as we get a resolved promise in tests.
+    setTimeout(function() {
+        parent.window.postMessage(msg, "*");
+    })
 </script>