The text direction attribute is now properly set for text runs in PDF.
It is inferred by the position of the first and the last characters of
a text run.

This change includes a pdf-template file (text-direction.in) with RTL
text representation used to generate our unit test PDF file.

Bug: 985604
Change-Id: If5d82296463331e95c4ded4e5244d65be3fbadfa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1737019
Commit-Queue: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#690163}