Implement MediaKeySession.generateRequest()

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

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
index d51ece0ce0a837d136de62e507cc2c3d4c068555..404a7428de76dd7c8a80b2b1ef5dce475b24a3da 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
@@ -39,21 +39,21 @@
                     assert_equals(numActiveDOMObjectsCreated(), 0, 'MediaKeys.create()');
 
                     // Create 3 sessions.
-                    return mediaKeys.createSession(initDataType, initData);
-                }).then(function(result) {
-                    mediaKeySession1 = result;
+                    mediaKeySession1 = mediaKeys.createSession();
+                    return mediaKeySession1.generateRequest(initDataType, initData);
+                }).then(function() {
                     assert_true(mediaKeySession1.sessionId && mediaKeySession1.sessionId.length > 0);
                     // Should be 1 MediaKeySession.
                     assert_equals(numActiveDOMObjectsCreated(), 1, 'mediaKeys.createSession(1)');
-                    return mediaKeys.createSession(initDataType, initData);
-                }).then(function(result) {
-                    mediaKeySession2 = result;
+                    mediaKeySession2 = mediaKeys.createSession();
+                    return mediaKeySession2.generateRequest(initDataType, initData);
+                }).then(function() {
                     assert_true(mediaKeySession2.sessionId && mediaKeySession2.sessionId.length > 0);
                     // Should be 2 MediaKeySessions.
                     assert_equals(numActiveDOMObjectsCreated(), 2, 'mediaKeys.createSession(2)');
-                    return mediaKeys.createSession(initDataType, initData);
-                }).then(function(result) {
-                    mediaKeySession3 = result;
+                    mediaKeySession3 = mediaKeys.createSession();
+                    return mediaKeySession3.generateRequest(initDataType, initData);
+                }).then(function() {
                     assert_true(mediaKeySession3.sessionId && mediaKeySession3.sessionId.length > 0);
                     // Should be 3 MediaKeySessions.
                     assert_equals(numActiveDOMObjectsCreated(), 3, 'mediaKeys.createSession(3)');