Migrate the most important tools (debugger, inspector, console) to the new
multi-process-aware architecture inside the Browser Toolbox.
This allows us to prepare DevTools for Fission, while making the Browser Toolbox (and the Browser Console) much more useful to Mozilla engineers.
Make the necessary changes for the Content Toolbox to support Fission.
Get all tools ready to support navigation process switches.
Stop relying on the <iframe mozbrowser> element, and embed RDM in the browser front-end code directly.