[Android WebView] Fix bots: add WebAuthN api interfaces to exclusion list

WebAuthN api should not be exposed in WebView.

BUG=828168
TBR=changwan@chromium.org,perezju@chromium.org
NOTRY=true

Change-Id: Ibe54d6785183bc0aaa557bf3de850e02b58b1f0c
Reviewed-on: https://chromium-review.googlesource.com/992272Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547678}

android_webview/tools/system_webview_shell/test/data/webexposed/not-webview-exposed.txt

@@ -80,6 +80,12 @@ interface MediaDevices : EventTarget
     getter ondevicechange
     setter ondevicechange
 
+# WebAuthN API should not be exposed in WebView, crbug.com/828168
+interface AuthenticatorAssertionResponse : AuthenticatorResponse
+interface PublicKeyCredential : Credential
+interface AuthenticatorResponse
+interface AuthenticatorAttestationResponse : AuthenticatorResponse
+
 [GLOBAL OBJECT]
     method openDatabase
     attribute eventSender                    # test only