Add Kerberos support to webview

Add negotiate handler to WebView's http auth handlers and
adds support for the policies (AuthAndroidNegotiateAccountType and
AuthServerWhitelist) required to configure Kerberos in WebView

BUG=533513

Review URL: https://codereview.chromium.org/1431473004

Cr-Commit-Position: refs/heads/master@{#361878}
9 files changed