Implement navigator.requestMediaKeySystemAccess()

Source/modules/encryptedmedia/MediaKeySystemAccess.idl

Index: Source/modules/encryptedmedia/MediaKeySystemAccess.idl
diff --git a/Source/modules/encryptedmedia/MediaKeySystemAccess.idl b/Source/modules/encryptedmedia/MediaKeySystemAccess.idl
new file mode 100644
index 0000000000000000000000000000000000000000..2da7487f7bb2611d75063185f04b5ebefc211ade
--- /dev/null
+++ b/Source/modules/encryptedmedia/MediaKeySystemAccess.idl
@@ -0,0 +1,14 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://dvcs.w3.org/hg/html-media/raw-file/default/encrypted-media/encrypted-media.html#mediakeysystemaccess-interface
+
+[
+    RuntimeEnabled=EncryptedMedia,
+    GarbageCollected,
+    TypeChecking=Interface
+] interface MediaKeySystemAccess {
+    readonly attribute DOMString keySystem;
+    [CallWith=ScriptState] Promise createMediaKeys();
+};