Add WebAuthn bindings and client interface.

third_party/WebKit/Source/modules/webauth/NavigatorAuth.idl

Index: third_party/WebKit/Source/modules/webauth/NavigatorAuth.idl
diff --git a/third_party/WebKit/Source/modules/webauth/NavigatorAuth.idl b/third_party/WebKit/Source/modules/webauth/NavigatorAuth.idl
new file mode 100644
index 0000000000000000000000000000000000000000..d27a730fcde4c173c1173835d7ef19e5aba52ea2
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+++ b/third_party/WebKit/Source/modules/webauth/NavigatorAuth.idl
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+// Copyright 2016 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://w3c.github.io/webauthn/#web-authentication-api
+
+partial interface Navigator {
+    [RuntimeEnabled=WebAuth] readonly attribute WebAuthentication authentication;
+};