ninja: error: '../../chrome/test/data/webui/mojo/foobar.mojom', needed by 'gen/chrome/test/data/webui/mojo/foobar.mojom-shared-message-ids.h', missing and no known rule to make it
This is caused by https://chromium.googlesource.com/chromium/src/+/2b09b8221d07f6a13569f0358c6dbc721bed2d59 and would require patching https://cs.chromium.org/chromium/build/scripts/slave/recipe_modules/chromium/resources/export_tarball.py to add the missing file. At present I'm having issues submitting CLs, so I'll defer to whoever picks it up first.
Thanks,
Olivier