They don't seem to have anything akin to Chrome's mobile emulator. They have "Responsive Design View" but it is much less feature complete than Chrome's mobile emulator, only seems to set a resolution.
If you launch WebIDE, you'll see that it can install Firefox OS emulators. I think it can connect with an Android emulator, too, but I haven't checked.
/me Loves Chrome Dev tools, anything less is a waste of time...