[LayoutNG] Remove LayoutNGPaintFragments flag

Remove the LayoutNGPaintFragments and instead have the existing LayoutNG
flag enable both LayoutNG and fragment painting as both have been on for
the bot for quite awhile now. This simplifies local testing and allow us
to remove the code for populating a LayoutInline with BiDi and text runs
which never worked quite as well as we would have linked.

Bug: 591099
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_layout_ng;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: If678572523ef02b429625d859ef5df5759e5ddfe
Reviewed-on: https://chromium-review.googlesource.com/905398
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Reviewed-by: Aleks Totic <atotic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535074}
41 files changed