Issue #2361 - Base implementation of Navigator.Clipboard

This hard-refuses any reads from clipboard with a promise rejection.

dom/webidl/Clipboard.webidl

@@ -0,0 +1,25 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * The origin of this IDL file is
+ * http://www.w3.org/TR/geolocation-API
+ *
+ * Copyright © 2018 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
+ * liability, trademark and document use rules apply.
+ */
+
+
+[SecureContext, Exposed=Window, Pref="dom.events.asyncClipboard"]
+interface Clipboard : EventTarget {
+  [Pref="dom.events.asyncClipboard.dataTransfer", Throws, NeedsSubjectPrincipal]
+  Promise<DataTransfer> read();
+  [Throws, NeedsSubjectPrincipal]
+  Promise<DOMString> readText();
+  [Pref="dom.events.asyncClipboard.dataTransfer", Throws, NeedsSubjectPrincipal]
+  Promise<void> write(DataTransfer data);
+  [Throws, NeedsSubjectPrincipal]
+  Promise<void> writeText(DOMString data);
+};
+