This runs `gn gen --check` with default args to detect mismatches between #includes and dependencies in the BUILD.gn files, as well as general build errors. Run this before uploading a CL for early detection, otherwise such errors will cause per-platform try jobs to fail. Bug: webrtc:8279 Change-Id: Ib87e2e3f40b8d1146ea5c1202fb113508a3f05e3 Reviewed-on: https://webrtc-review.googlesource.com/5482 Commit-Queue: Oleh Prypin <oprypin@webrtc.org> Reviewed-by: Henrik Kjellander <kjellander@webrtc.org> Reviewed-by: Patrik Höglund <phoglund@webrtc.org> Reviewed-by: Edward Lemur <ehmaldonado@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20208}