Update HistoryController::current_entry_ on all main frame back/forwards.

This fixes a case where it was left stale on a cross-origin commit
because the provisional_entry_ had been cleared by a different commit.

BUG=623319
TEST=See bug comment 14 for repro steps.
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2134493002
Cr-Commit-Position: refs/heads/master@{#404537}
(cherry picked from commit ab22bdfc5cb681f2f4dc789171e97618a9657486)

Review URL: https://codereview.chromium.org/2149203002 .

Cr-Commit-Position: refs/branch-heads/2743@{#629}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}
2 files changed