In order to enable adb-over-USB in developer mode in Chrome OS, we need to do several steps in the console:

$ sudo crossystem dev_enable_udc=1
$ sudo reboot

And then every time the feature wants to be used,

$ sudo ectool usbpd <port number> dr_swap

So two new entries should be added to chrome://settings, one that sends a D-Bus message to debugd that performs the first setup and shows a dialog that prompts the user to reboot (description of that below), and another one that sends a D-Bus message to debugd that performs the second one.

After discussing with shihuis@, the following was suggested for the dialog:

* Stick close w/ the powerwash dialogue for Chrome OS as possible since that's for reboot as well.
* Using the powerwash is also desired since it's the Chrome OS UI instead of Android and you'll be rebooting the entire machine so it's more relevant.


Text
Title: "Restart your device"
Whatever disclaimer security tells you say to the user like "this makes the device more vulnerable, etc"
"A restart is required before your device an use [adb over usb]."

Buttons
Cancel
Restart

To confirm, when you click CANCEL on this dialogue, does the adb entry in the settings stay turned on or become turned off again? My 2c is that it's the latter so users know exactly that they need to restart for this and don't forget.