code: async function showExtensionTab(url, match = url) {
  	match = extension.getURL(match || url); url = extension.getURL(url);
  	for (const view of extension.getViews({ type: 'tab', })) {
  		if (view && (typeof match === 'string' ? view.location.href === match : match.test(view.location.href)) && view.tabId != null) {
  			const tab = (await new Promise(got => (view.browser || view.chrome).tabs.getCurrent(got)));
  			if (tab) { (await Tabs.update(tab.id, { active: true, })); (await Windows.update(tab.windowId, { focused: true, })); return tab; }
  		}
  	}
  	return Tabs.create({ url, });
  }
docs: Shows or opens a tab containing an extension page.
  Shows the fist tab whose .pathname equals 'match' and that has a window.tabId set, or opens a new tab containing 'url' if no such tab is found.
  @param  {string}        url    The url to open in the new tab if no existing tab was found.
  @param  {string}        match  Optional value of window.location.pathname a existing tab must have to be focused.
  @return {Promise<Tab>}         The chrome.tabs.Tab that is now the active tab in the focused window.