[build] Add ability to define manifest package in GN

The build system will verify that the manifest packages match if you
specify it in both GN and the manifest.

Bug: 891996
Change-Id: I39c3f158d01908b971a3ef47cb90af73019284a0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1667687
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#671814}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5172118ff57bef7dd2864c9fe891db9c05f76a2b
2 files changed