Remove exponential growth of MarkerType enum values

Mojo supports enum value assignments, so there's no point in keeping around every combination of MarkerType.
TBR=dcheng@chromium.org

Test: accessibility_unittests
Change-Id: I4e0602eb92a933f18a8b837b8bfc54fedfc9eb62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1943052
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720808}
3 files changed