The two root causes are angleproject:3695 and angleproject:3836.  Some tests
failing from angleproject:3836 were still labeled for angleproject:3458.  This
CL does some cleanup of that, and improves the comments for the two
root-causes.

Bug: angleproject:3188
Bug: angleproject:3458
Bug: angleproject:3695
Bug: angleproject:3836
Change-Id: I4c9be0b3078c1fc21064fb88b58e28ea92c3a73c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1834275Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Ian Elliott <ianelliott@google.com>