src/vs/workbench/contrib/terminal/browser/terminalInstance.ts/TerminalInstance/_setFocus
class TerminalInstance:	private _setFocus(focused?: boolean): void {
		if (focused) {
			this._terminalFocusContextKey.set(true);
			this._onDidFocus.fire(this);
		} else {
			this._terminalFocusContextKey.reset();
			this._onDidBlur.fire(this);
			this._refreshSelectionContextKey();
		}
	}