When showing an OutputChannel, it will steal the current focus. In an atempt to be less disruptive and keep the user's current focus, I tried the following code:

let textDocument = vscode.window.activeTextEditor.document;
let channel = vscode.window.createOutputChannel('test');
channel.show(2);
vscode.window.showTextDocument(textDocument);

This returns the focus to the previously focused document, but it has one quirk, when any quick panel is opened and then closed, the focus will go to the OutputChannel instead of going to the previously focused document.