These are scripts that can be useful to run independently as you're working on Chrome DevTools front-end.
The newer scripts such as for testing and hosted mode are written in Node.js, which has become the standard toolchain for web apps. The older scripts such as building (e.g. bundling and minifying) are written in Python, which has first-class support in Chromium's infrastructure.
The easiest way to run the node.js scripts is to use
npm run which displays all the commands. For more information on the specific
npm run commands, take a look at the primary devtools front-end readme (
DevTools manually rolls the closure compiler to ./closure. If you manually roll closure compiler, you will need to re-generate the closure_runner (in ./closure) and jsdoc_validator custom jars using the python scripts in their respective directory.