Remove HostWindow::scroll and ChromeClient::scroll.

These don't seem to be doing anything important.

Review URL: https://codereview.chromium.org/498593002

git-svn-id: svn://svn.chromium.org/blink/trunk@180824 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove resetScrollbars

This is ancient code that appears to now be unnecessary. All tests pass
when it's removed.

BUG=403814

Review URL: https://codereview.chromium.org/454023002

git-svn-id: svn://svn.chromium.org/blink/trunk@180825 bbb929c8-8fbe-4397-9dbb-9b2b20218538