async activate(oPort) {
			oCurrentPort = oPort;

			if (this._isActive) { return; }

			this._isActive = true;
			await init();
			// need to register for both focusin and focusout event
			// Browser fires:
			//  * only focusin when focus is moved from <body> to a focusable element
			//  * only focusout when focus is moved from a focused element to <body>
			//  * first focusout then focusin when moved from a focused element to another focusable element
			document.addEventListener("focusin", init);
			document.addEventListener("focusout", init);
		}
Activates the keyboard interaction information gathering.
This methods starts listening for focusin and focusout events to gather the keyboard interaction information.

@param  {MessagePort} oPort The MessagePort used to send the keyboard interaction information.
@private