SingleProcessMash: Fix window size after display zoom

aura::TopLevelAllocator::NotifyServerOfLocalSurfaceId() needs to pass
bounds in DIPs, not pixels.

Also clarify dips vs. pixels in some function parameters and member
variables.

TBR=tsepez@chromium.org

Bug: 934180

Change-Id: I28b0331f9d430e195f37b9a73061fc831b40f44f
Reviewed-on: https://chromium-review.googlesource.com/c/1479889
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634388}
8 files changed