GitLab

Duplicates configs defined in //build/config/mac/BUILD.gn that
are shared with iOS to //build/config/ios/BUILD.gn. Remove all
conditions testing "is_mac" or "is_ios" (as they are now known
from the filename).

Change dependencies on previously shared targets to select the
correct target based on the "target_os".

BUG=635745

Review-Url: https://codereview.chromium.org/2843493002
Cr-Commit-Position: refs/heads/master@{#467680}