Clear provisional item on all server redirects.

Whether a redirect is cross-origin or not, the result will be a new
document and should not reuse the provisional HistoryItem during a
back/forward navigation.

BUG=585194
TBR=clamy
TEST=http/tests/navigation/back-to-redirect-with-frame.php
     in --isolate-sites-for-testing mode.

Review-Url: https://codereview.chromium.org/2159093002
Cr-Commit-Position: refs/heads/master@{#406861}
4 files changed