use activeTab for getting active tab info from popup

[tomholub]

We're trying to stop using the tabs permission if we can, in order to show less scary permissions when user is installing the browser extension. tabs permission causes Can read data on all websites warning, which is not what the extension actually does.

One way we use .tabs is to get information about active tab:

  public static getActiveTabInfo: Bm.AsyncRespondingHandler = () => new Promise((resolve, reject) => {
    chrome.tabs.query({ active: true, currentWindow: true, url: ["*://mail.google.com/*", "*://inbox.google.com/*"] }, (activeTabs) => {
      if (activeTabs.length) {
        if (activeTabs[0].id !== undefined) {
          type ScriptRes = { acctEmail: string | undefined, sameWorld: boolean | undefined }[];
          chrome.tabs.executeScript(activeTabs[0].id!, { code: 'var r = {acctEmail: window.account_email_global, sameWorld: window.same_world_global}; r' }, (result: ScriptRes) => {
            resolve({ provider: 'gmail', acctEmail: result[0].acctEmail, sameWorld: result[0].sameWorld === true });
          });
        } else {
          reject(new Error('tabs[0].id is undefined'));
        }
      } else {
        resolve({ provider: undefined, acctEmail: undefined, sameWorld: undefined });
      }
    });
  })

They say, for this we can instead use activeTab permission from the popup, which does not cause warning (meaning it should not cause app disabling either), see https://developer.chrome.com/extensions/activeTab

Originally posted by @tomholub in #2497 (comment)

[tomholub]

Could you take a look? This one is a bit more advanced (specific to browser extensions).

[tomholub]

Sorry, I've moved it down in priority, and will evaluate it when the time comes to it, by which time some things may change.