GitLab

This could happen in cases where we initiate a transfer but end up navigating
in the original SiteInstance.

BUG=402018
TEST=No proxy host for the current RFH after navigating an about:blank tab.

Review URL: https://codereview.chromium.org/452673002

Cr-Commit-Position: refs/heads/master@{#288406}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288406 0039d316-1c4b-4281-b951-d872f2087c98