cc: Fix high/low res scale collisions
If a tree doesn't support low res, but it turns out that a pre-existing
tiling just happens to be at the low res scale, it will treat it as low
res. Since the pending tree only cleans up non-ideal scales, this low
res tiling sticks around and causes asserts.
R=vmpstr@chromium.org,danakj@chromium.org
BUG=469176
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
Review URL: https://codereview.chromium.org/
1210073021
Cr-Commit-Position: refs/heads/master@{#337458}