GitLab

Enums in Mojo have |kMaxValue| automatically defined. Switch
PdfCompositor UMAs to use the 2-parameter UMA_HISTOGRAM_ENUMERATION
macro, which uses |kMaxValue|, and avoid the need for static_casts with
the 3-parameter UMA_HISTOGRAM_ENUMERATION variant.

Along the way, switch the PdfCompositor enum to kFoo style, and fix a
typo to stop referring to composting.

BUG=742517

Change-Id: Id9664371d3b2d7b0fe1203069d96c37b3e4b41de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1661490Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669957}