Convert Chrome manifest overlays to C++

This deletes Chrome's JSON service manifest overlays and builds them
instead as C++ Manifest objects.

Bug: 895616
Change-Id: I86f7a58c555239d97f809e2ae9f05c429b2bfe2f
Reviewed-on: https://chromium-review.googlesource.com/c/1401507
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#622200}
33 files changed