Change MediaKeys.setServerCertificate() to return Promise<boolean>

third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html

Index: third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html
diff --git a/third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html b/third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html
index 8e3058b7c3dde38f4aeb8cc134e2e96adf5e637f..98e66e7a5c683d72368587343d6166906bed1801 100644
--- a/third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html
+++ b/third_party/WebKit/LayoutTests/media/encrypted-media/encrypted-media-async-setcert-with-gc.html
@@ -19,11 +19,8 @@
                 }).then(function(mediaKeys) {
                     var cert = new Uint8Array(200);
                     return mediaKeys.setServerCertificate(cert);
-                }).then(function() {
-                    assert_unreached('setServerCertificate() did not fail');
-                }, function(e) {
-                    assert_equals(e.name, 'NotSupportedError');
-                    return Promise.resolve();
+                }).then(function(result) {
+                    assert_false(result);
                 });

[ddorwin, 2016/06/13 17:28:09]

Do we need something like this here to catch an incorrect rejection? This
appears to pass without a done() call in the expected path.
.catch(function(error) {
  forceTestFailureFromPromise

[jrummell, 2016/06/13 18:54:13]

This is a promise_test(), so it fails if the promise fails. The older tests use
async_test(), where we need to fail the test if the promise is rejected.

             }, 'Test asynchronous setServerCertificate while running garbage collection.');
         </script>