web_dev_style: discourage CSS *-left/right properties and values

Instead, suggest equivalent *-start/end values that automatically
flip in RTL.  For example, if the presubmit finds something along
the lines of:

  margin-left: 5px;

It'll flag it and encourage the directionally-aware:

  margin-inline-start: 5px;

Unless annotated with:

  margin-left: 5px;  /* csschecker-disable-line left-right */

for code that's truly direction agnostic.

R=dpapad@chromium.org
BUG=921226

Change-Id: If649c4eed125af4dfd5cb8b3284dc1c900230847
Reviewed-on: https://chromium-review.googlesource.com/c/1407787
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623096}
2 files changed