As a follow up to Bug 1302702, when a webextension is running in oop mode, we can attach it using a regular toolbox (which runs in the main process, the same process of the browser itself) instead of using the BrowserToolboxProcess (which is needed to create a separate process to attach and debug an extension when it is running in the main process). By using a regular toolbox we will be able to overcome some of the current limitations due to the need of using the BrowserToolboxProcess for the Addon Debugging toolbox: - opening the Addon Debugging toolbox will be way faster, because it doesn't need to spawn a new process and load all the developer tools internals (and a good amount of Firefox internals) in the new process (and the user will not need to accept the connection to the debugger explicitly everytime an Addon Debugging toolbox is opened) - opening more than one Addon Debugging toolbox at the same time (or open an Addon Debugger toolbox alongside a Browser Toolbox), which is not currently possible because because of some limitations in the BrowserToolboxProcess - being able to more easily "enabling devtools panels provided by a webextension on the "WebExtensions Addon Debugging toolbox" (e.g. because we will not need to "install and enable" the devtools addons into the separate profile that the BrowserToolboxProcess creates)