GitLab

Rather than override the caption bubble's view accessibility with
virtual children, override the label's view accessibility with a
different AXNode per line. This allows us to take advantage of the
views' visibility and bounds--whereas previously we needed to keep track
of whether the error was visible or not.

This CL also renames functions and variables from virtual_children to
ax_lines. It sets the label role to be kParagraph and each ax_line role
to be kStaticText.

Bug: 1055150
Change-Id: Ic70187b1e0159d4fa012bc44e1ec40b2357717e8
AX-Relnotes: N/A (Feature has not launched)
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2602660Reviewed-by: Josiah Krutz <josiahk@google.com>
Commit-Queue: Abigail Klein <abigailbklein@google.com>
Cr-Commit-Position: refs/heads/master@{#839778}