[layoutng] Override computeIntrinsicLogicalWidths so we can use the NG code for it

This is mostly straightforward, except that on Mac, we may have to
compute intrinsic sizes outside of layout. So this patch also adds
special code to avoid layout calls in such cases (for orthogonal
flows). However, this also required me to change some tests to have
the correct "inside of layout" state.

Notes on tests:
  fast/dynamic/012.html
    Had an incorrect rebaseline; rendering matches legacy modulo
    text splitting (positioning is the same)

  css2.1/20110323/table-height-algorithm-023.htm
  css2.1/20110323/table-height-algorithm-024.htm
    Parts of these tests were already using the smaller size due to
    1px text rendering differences; this rebaseline just makes us
    more consistent.

  tables/mozilla/bugs/bug57828.html
    Also a trivial 1px difference

  tables/mozilla/bugs/bug60992.html
    Probably an issue of bug 40634; legacy takes the whitespace before
    <br> (here, a linebreak) into account for calculating the width
    of the cell and NG does not.

  tables/mozilla_expected_failures/bugs/bug1010.html
    Also 1px and 2px text rendering difference

  virtual/layout_ng_experimental/external/wpt/css/css-flexbox/flexbox_stf-table-caption.html
    Fails for an unrelated reason, see newly filed bug 857185

Bug: 635619
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Ia11317acd777aec201702fce28ebab74dba99b4f
Reviewed-on: https://chromium-review.googlesource.com/508293
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570953}
23 files changed