GitLab

This is a follow up to crrev.com/c/2254319

By using the layout constants instead of the hard coded values.

For the combobox, this however affects only Mac
The reason for that is on Mac both
config.icons_in_label and type_ == Type::kCheckbox evaluated to true.
while on Linux both were false.

Screenshots:
Before: https://screenshot.googleplex.com/YC96zjVu2Cx
After: https://screenshot.googleplex.com/Uusea7yG6wd

Bug: 1044038
Change-Id: I20ee4e2aa416e0405df7a660e419b2b3a01e16e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2264335Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782016}