Use requestMediaKeySystemAccess() to check type support in EME layout tests

LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html

Index: LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html b/LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html
index 1c8493bb78c806b4ff8f885720b4a8afe5d0d281..44dc6f334d992b4f0f76f2ec3461376441eacfed 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-keystatuses.html
@@ -10,6 +10,8 @@
         <div id="log"></div>
         <script>
             var mediaKeySession;
+            var initDataType;
+            var initData;
 
             // Even though key ids are uint8, using printable values so that
             // they can be verified easily.
@@ -98,17 +100,20 @@
                     test.done();
                 }
 
-                navigator.requestMediaKeySystemAccess('org.w3.clearkey', [{}]).then(function(access) {
+                getSupportedInitDataType().then(function(type) {
+                    initDataType = type;
+                    initData = getInitData(initDataType);
+                    return navigator.requestMediaKeySystemAccess('org.w3.clearkey', [{}]);
+                }).then(function(access) {
                     return access.createMediaKeys();
                 }).then(function(mediaKeys) {
-                    var initDataType = getInitDataType();
                     mediaKeySession = mediaKeys.createSession();
 
                     // There should be no keys defined yet.
                     assert_equals(mediaKeySession.keyStatuses.size, 0);
 
                     waitForEventAndRunStep('message', mediaKeySession, processMessage, test);
-                    return mediaKeySession.generateRequest(initDataType, getInitData(initDataType));
+                    return mediaKeySession.generateRequest(initDataType, initData);
                 }).catch(function(error) {
                     forceTestFailureFromPromise(test, error);
                 });