notif - use standard err-first callback style

app/scripts/lib/notifications.js

@@ -9,13 +9,17 @@ module.exports = notifications
 window.METAMASK_NOTIFIER = notifications
 
 function show () {
-  getWindows((windows) => {
+  getPopup((err, popup) => {
+    if (err) throw err
 
-    if (windows.length > 0) {
-      const win = windows[0]
-      return extension.windows.update(win.id, { focused: true })
-    }
+    if (popup) {
+
+      // bring focus to existing popup
+      extension.windows.update(popup.id, { focused: true })
+
+    } else {
 
+      // create new popup
       extension.windows.create({
         url: 'notification.html',
         type: 'popup',
@@ -23,6 +27,8 @@ function show () {
         width: 360,
         height: 500,
       })
+
+    }
   })
 }
 
@@ -38,19 +44,19 @@ function getWindows(cb) {
 }
 
 function getPopup(cb) {
-  getWindows((windows) => {
-    cb(getPopupIn(windows))
+  getWindows((err, windows) => {
+    if (err) throw err
+    cb(null, getPopupIn(windows))
   })
 }
 
 function getPopupIn(windows) {
-  return windows ? windows.find((win) => {
-    return win.type === 'popup'
-  }) : null
+  return windows ? windows.find((win) => win.type === 'popup') : null
 }
 
 function closePopup() {
-  getPopup((popup) => {
+  getPopup((err, popup) => {
+    if (err) throw err
     if (!popup) return
     extension.windows.remove(popup.id, console.error)
   })