Extension API: chrome.windows.onFocusChanged

[jonathansampson]

Describe the issue you encountered:
The chrome.windows.onFocusChanged API is not presently supported. As a result, the following throws:

      chrome.windows.onFocusChanged.addListener((function(_this) {
        return function(wnd) {
          if (wnd !== chrome.windows.WINDOW_ID_NONE) {
            return chrome.tabs.query({
              windowId: wnd,
              active: true
            }, function(tabs) {
              if (tabs[0]) {
                return _this.register(tabs[0].id);
              }
            });
          }
        };
      })(this));

Expected behavior:
Brave should be able to inform Vimium when the window has lost focus.

Blocked Extensions

• Extension: Vimium #9531 Vimium

[jonathansampson]

Dupe of #4760