AW docs: class verification explainer

No change to logic, only docs.

This adds an explainer for class verification (focusing on ART), and
tips for debugging class verification errors, including
list_class_verification_failures.py.

Bug: 918221, 855796
Test: tools/md_browser/md_browser.py
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: I28c0e5fb337fe0f126106b6e5bc6a5001ce24167
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1663589
Reviewed-by: Changwan Ryu <[email protected]>
Reviewed-by: Andrew Grieve <[email protected]>
Commit-Queue: Nate Fischer <[email protected]>
Cr-Commit-Position: refs/heads/master@{#671900}
1 file changed