Remove children from HistoryNodes that redirect during back/forward navigation

Failing to do so can lead to spurious HistoryNodes ending up in the HistoryEntry
for the destination of the redirect. If we try to restore that HistoryEntry, we
might try to use the wrong HistoryNode and break the page.

BUG=334598
TEST=http/tests/navigation/back-to-redirect-with-frame.html

Review URL: https://codereview.chromium.org/141013013

git-svn-id: svn://svn.chromium.org/blink/trunk@165356 bbb929c8-8fbe-4397-9dbb-9b2b20218538