As we are encouraging to use GN to build Chrome, I am following the instructions as:
gn gen out/Default --args='target_os="chromeos"'
export GYP_CHROMIUM_NO_ACTION=1

I find my updates in the following directory:
src/sync/protocol/
is not respected, A linker error happens when I run

ninja -C out/Debug sync_unit_tests

The file: sync/protocol/arc_package_specifics.proto which I add in the CL: https://codereview.chromium.org/2092893002/ is marked as undefined reference.

And it works fine if I do:
export GYP_CHROMIUM_NO_ACTION=0
python build/gyp_chromium
ninja -C out/Debug sync_unit_tests

I am wondering if it is a builder migration issue.