In order for us to quickly iterate on Flutter for web, we need to be able to quickly debug changes we make both in the web engine and in the framework. Currently, this requires a non-trivial manual sequence of commands involving gn, ninja, and flutter_tools, executed at the right moment.

Let's build a contributor-only dev tool that encapsulates this complexity.

/cc @mdebbar this is about your upcoming felt build --watch tool. I'm filing it so we can track progress as part of the "Flutter for web infrastructure 2019" project. Feel free to adjust the labels as you see fit.

/cc @jonahwilliams this builds on the work you've already done in the flutter tool, but we may need your help if we encounter issues.