The Promoted* prefix was used to refer both to the total number of old
generation objects, and to the delta of objects moved from the new to
old generations.

PromotedTotalSize() is also renamed, to reflect the actual calculation
it performs

Bug: chromium:837583
Change-Id: Id27a0661618257ef64eb469a83bb49c0e8ce6923
Reviewed-on: https://chromium-review.googlesource.com/1042314
Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52986}