Add WebAuthn bindings and client interface.

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

Index: third_party/WebKit/Source/modules/webauth/AuthenticationAssertion.idl
diff --git a/third_party/WebKit/Source/modules/webauth/AuthenticationAssertion.idl b/third_party/WebKit/Source/modules/webauth/AuthenticationAssertion.idl
new file mode 100644
index 0000000000000000000000000000000000000000..16712494ffd9a9606c9dfc89cce51ac3ec54fc9b
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+++ b/third_party/WebKit/Source/modules/webauth/AuthenticationAssertion.idl
@@ -0,0 +1,15 @@
+// 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/#webauthnassertion
+
+[
+    RuntimeEnabled=WebAuth,
+    SecureContext
+] interface AuthenticationAssertion {
+    readonly attribute ScopedCredential credential;
+    readonly attribute ArrayBuffer clientData;
+    readonly attribute ArrayBuffer authenticatorData;
+    readonly attribute ArrayBuffer signature;
+};