base: remove BiDiLineIterator AS_URL support

This support was originally added to support a fix for issue 351639. That fix
turned out to be infeasible, at least for now, but the support code was never
removed. This change:

1) Removes the left-to-right-urls flag and backing feature;
2) Removes support for AS_URL from BiDiLineIterator, which was guarded by that
   feature;
3) Breaks the dependency from OmniboxResultView on BiDiLineIterator;
4) Moves BiDiLineIterator out of //base and into //ui/gfx, next to its only
   remaining client (RenderTextHarfBuzz).

Bug: 351639
Change-Id: I523adac66e3b53218080e5711486b315c3e1a128
Reviewed-on: https://chromium-review.googlesource.com/c/1464353
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631313}
16 files changed