Supports the sound attribute to the Notification object

LayoutTests/http/tests/notifications/notification-properties.html

Index: LayoutTests/http/tests/notifications/notification-properties.html
diff --git a/LayoutTests/http/tests/notifications/notification-properties.html b/LayoutTests/http/tests/notifications/notification-properties.html
index f54a903dc501b4142c5e42c88db5ef32ee43ea90..7c7702295a14dcf96e9855b0c31315b4206b5a3e 100644
--- a/LayoutTests/http/tests/notifications/notification-properties.html
+++ b/LayoutTests/http/tests/notifications/notification-properties.html
@@ -40,6 +40,7 @@
             assert_equals(emptyNotification.body, "");
             assert_equals(emptyNotification.tag, "");
             assert_equals(emptyNotification.icon, "");
+            assert_equals(notification.sound, "");
             assert_equals(notification.vibrate, null);
             assert_false(emptyNotification.silent);
             assert_equals(emptyNotification.data, null);
@@ -64,6 +65,28 @@
             // Setting an empty string as the tag should be equal to not setting the tag at all.
             assert_equals(noTagNotification.tag, emptyTagNotification.tag);
 
+            var invalidSoundNotification = new Notification("My Notification", {
+                sound: "http://test:test/test.mp3"
+            });
+
+            // Invalid sound URLs should be reset to an empty string.
+            assert_equals(invalidSoundNotification.sound, "");
+
+            var serializedSoundUrlNotification = new Notification("My Notification", {
+                sound: "http://example.com/example.mp3"
+            });
+
+            // Sound URLs should be returned in serialized form.
+            assert_equals(serializedSoundUrlNotification.sound, "http://example.com/example.mp3");
+
+            // Verifying the exception throwing behavior, when silent set true and sound is presented.
+            assert_throws(new TypeError(), function() {
+                var notification = new Notification("My Notification", {
+                    silent: true,
+                    sound: "http://example.com/example.mp3"
+                });
+            }, 'Set sound, when silent is true.');
+
             var vibrateNotification = new Notification("My Notification", {
                 vibrate: 1000
             });