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

LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html
index 1bb3edeea4624e5db3c85a15f0741f79b231780b..fad7a89234dcbfb4a2198cc9733c4c9ea415fe1b 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-multiple-mediakeys.html
@@ -28,9 +28,6 @@
             async_test(function(test)
             {
                 var mediaKeys;
-                var initDataType = getInitDataType();
-                var initData = getInitData(initDataType);
-
                 var startingActiveDOMObjectCount = window.internals.activeDOMObjectCount(document);
 
                 function numActiveDOMObjectsCreated()
@@ -44,7 +41,14 @@
                 // MediaKeySession object.
                 function createMediaKeyWithMediaKeySession()
                 {
-                    return navigator.requestMediaKeySystemAccess('org.w3.clearkey', [{}]).then(function(access) {
+                    var initDataType;
+                    var initData;
+
+                    return 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;