I glanced over it quickly. A lot of the code files are really small, a couple of lines each. The rest is a mixture of actual logic, boilerplate and integration

I glanced over it quickly. A lot of the code files are really small, a couple of lines each. The rest is a mixture of actual logic, boilerplate and integration overhead (mostly due to a lot of event based asynchronous task handling). The overhead comes with the territory when integrating something into a big codebase such as a browser. The business rules are still a few 100 lines, though.