Fix typo in Byte->MegaByte conversion.

Bug: b:151176984
Change-Id: I21cdb37edcc8880c86660393c7e4ed620e70fe89
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2397984


Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Daniil Lunev <dlunev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805596}