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

LayoutTests/media/encrypted-media/encrypted-media-events.html

Index: LayoutTests/media/encrypted-media/encrypted-media-events.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-events.html b/LayoutTests/media/encrypted-media/encrypted-media-events.html
index acd33dfd05b64c82331d74cdc4afad415d3990b7..917c902143e3acb336130570fc7c2170cee793dc 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-events.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-events.html
@@ -13,6 +13,7 @@
             // "keychange" events.
             async_test(function(test)
             {
+                var initDataType;
                 var mediaKeySession;
                 var rawKey = new Uint8Array([0xeb, 0xdd, 0x62, 0xf1, 0x68, 0x14, 0xd2, 0x7b,
                                              0x68, 0xef, 0x12, 0x2a, 0xfc, 0xe4, 0xae, 0x3c]);
@@ -42,10 +43,12 @@
                     test.done();
                 }
 
-                navigator.requestMediaKeySystemAccess('org.w3.clearkey', [{}]).then(function(access) {
+                getSupportedInitDataType().then(function(type) {
+                    initDataType = type;
+                    return navigator.requestMediaKeySystemAccess('org.w3.clearkey', [{}]);
+                }).then(function(access) {
                     return access.createMediaKeys();
                 }).then(test.step_func(function(mediaKeys) {
-                    var initDataType = getInitDataType();
                     mediaKeySession = mediaKeys.createSession();
                     waitForEventAndRunStep('message', mediaKeySession, test.step_func(processMessage), test);
                     return mediaKeySession.generateRequest(initDataType, getInitData(initDataType));

[sandersd (OOO until July 31), 2015/03/16 19:57:08]

Why not the usual pattern of fetching this after getSupportedInitDataType()?

[jrummell, 2015/03/16 20:44:09]

Probably the first file I changed. Done.