Merge to M44: When serializing accessibility tree, skip invalid children.
See bug for specific repro in the wild, but essentially we need to check
if the child is valid just before serializing, and not trust the list of
children of a node.
BUG=479743
Review URL: https://codereview.chromium.org/1144363004
Cr-Commit-Position: refs/heads/master@{#332748}
(cherry picked from commit 8dc07f045c6287da3404fa8e0fd8b1b3960afbfa)
Review URL: https://codereview.chromium.org/1161103004
Cr-Commit-Position: refs/branch-heads/2403@{#209}
Cr-Branched-From: f54b8097a9c45ed4ad308133d49f05325d6c5070-refs/heads/master@{#330231}
2 files changed
