The files in this directory control how tests are run on the Chromium buildbots. In addition to specifying what tests run on which builders, they also specify special arguments and constraints for the tests.
Logic in the Chromium recipe looks up each builder for each master and test generators in chromium_tests/steps.py parse the data. For example, as of a6e11220 generate_gtest parses any entry in a builder's ‘gtest_tests’ entry.
After editing any buildbot json, run ./manage.py -w to load and write in the canonical format. Then commit as normal.
Note that trybots mirror regular waterfall bots, with the mapping defined in trybots.py. This means that, as of 81fcc4bc, if you want to edit linux_android_rel_ng, you actually need to edit Android Tests.
You should be able to try build changes that affect the trybots directly (for example, adding a test to linux_android_rel_ng should show up immediately in your tryjob). Non-trybot changes have to be landed manually :(.
When adding tests or bumping timeouts in the buildbot configuration json, care must be taken to ensure the infrastructure has capacity to handle the extra load. This is especially true for the established Chromium CQ builders, as they operate under strict execution requirements. Make sure to get an infrastructure engineer on the Crossover Team to sign off that there is both buildbot and swarming capacity available.