Update playbackRate tests to check for behavior when set to an unsupp…

…orted value

See whatwg/html#2829 for HTML Standard change.

html/semantics/embedded-content/media-elements/playing-the-media-resource/playbackRate.html

@@ -9,11 +9,46 @@
   assert_equals(v.playbackRate, 1);
 }, 'playbackRate initial value');
 
-async_test(function(t) {
+function testPlaybackRateHelper(t, newPlaybackRate) {
   var v = document.createElement('video');
-  v.playbackRate = 2;
-  v.addEventListener('ratechange', t.step_func(function() {
+  var initialRate = v.playbackRate;
+
+  v.addEventListener('ratechange', function() {
+    assert_equals(v.playbackRate, newPlaybackRate);
     t.done();
-  }));
-}, 'setting playbackRate');
+  });
+
+  try {
+    v.playbackRate = newPlaybackRate;
+  } catch(e) {
+    assert_equals(e.name, 'NotSupportedError');
+    assert_equals(v.playbackRate, initialRate);
+    t.done();
+  }
+}
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, 3);
+}, "playbackRate set to small positive value");
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, 100);
+}, "playbackRate set to large positive value");
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, -3);
+}, "playbackRate set to small negative value");
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, -100);
+}, "playbackRate set to large negative value");
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, 0);
+}, "playbackRate set to 0");
+
+async_test(function(t) {
+  testPlaybackRateHelper(this, -1);
+}, "playbackRate set to -1");
+
 </script>