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

LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html
index 390042257d59a458df21b58e8905f4180bb9c0ed..4d745f0a39a19b3188e4b7a716b524ac14190579 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-release.html
@@ -20,8 +20,8 @@
                 var mediaKeys;
                 var mediaKeySession1;
                 var mediaKeySession2;
-                var initDataType = getInitDataType();
-                var initData = getInitData(initDataType);
+                var initDataType;
+                var initData;
                 var startingActiveDOMObjectCount = window.internals.activeDOMObjectCount(document);
 
                 function numActiveDOMObjectsCreated()
@@ -30,7 +30,11 @@
                 }
 
                 // Create 2 sessions.
-                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(result) {
                     mediaKeys = result;