GitLab

List items in Android settings are:
1. clickable
2. have no content description
3. contain text nodes (possibly multiple)

Fixes:
1. never consider clickables as containers. ChromeVox has logic to descend into containers. For ordinary list items on the web, we usually want to treat them as containers because list items have arbitrarily nested complex structures (e.g. links, headings inside).
2. fix the computation of list item name. Previously, we only computed the name based on a tree walker that visits and stops descent into leafs or static text. Since clickables themselves are leaves, this stopped the walker from descending into the children of the list item.

Bug: b:118842617
Test: manually on ARC++ settings. Regression coverage provided by browser_tests --gtest_filter=ChromeVox*.*
Change-Id: I916c2a4187502c19d489e7c78e965523c05f6074
Reviewed-on: https://chromium-review.googlesource.com/c/1316095
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Yuki Awano <yawano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605264}