Windows/Linux: Fix broken Quit option in Tray icon

This also cleans up the code by handling quit in the same way for all
platforms, removing the special case in tray.js for darwin.

We already have a 'before-quit' handler in main/index.js, so this is
now handled there :)

main/index.js

@@ -1,6 +1,7 @@
 var electron = require('electron')
 
 var app = electron.app
+var ipcMain = electron.ipcMain
 
 var autoUpdater = require('./auto-updater')
 var config = require('../config')
@@ -62,8 +63,14 @@ function init () {
     processArgv(argv)
   })
 
-  app.on('before-quit', function () {
+  app.on('before-quit', function (e) {
+    if (app.isQuitting) return
+
     app.isQuitting = true
+    e.preventDefault()
+    windows.main.send('dispatch', 'saveState') /* try to save state on exit */
+    ipcMain.once('savedState', () => app.quit())
+    setTimeout(() => app.quit(), 2000) /* quit after 2 secs, at most */
   })
 
   app.on('activate', function () {

main/tray.js

@@ -4,20 +4,20 @@ module.exports = {
 
 var path = require('path')
 var electron = require('electron')
+
+var app = electron.app
+var Menu = electron.Menu
+var Tray = electron.Tray
+
 var windows = require('./windows')
 
 var trayIcon
 
 function init () {
-  if (process.platform === 'darwin') {
-    // Instead of relying on the tray icon quit button, listen for Cmd+Q
-    electron.app.once('before-quit', quitApp)
+  // OS X has no tray icon
+  if (process.platform === 'darwin') return
 
-    // OS X has no tray icon
-    return
-  }
-
-  trayIcon = new electron.Tray(path.join(__dirname, '..', 'static', 'WebTorrentSmall.png'))
+  trayIcon = new Tray(path.join(__dirname, '..', 'static', 'WebTorrentSmall.png'))
 
   // On Windows, left click to open the app, right click for context menu
   // On Linux, any click (right or left) opens the context menu
@@ -36,9 +36,9 @@ function updateTrayMenu () {
   } else {
     showHideMenuItem = { label: 'Show', click: showApp }
   }
-  var contextMenu = electron.Menu.buildFromTemplate([
+  var contextMenu = Menu.buildFromTemplate([
     showHideMenuItem,
-    { label: 'Quit', click: quitApp }
+    { label: 'Quit', click: () => app.quit() }
   ])
   trayIcon.setContextMenu(contextMenu)
 }
@@ -50,10 +50,3 @@ function showApp () {
 function hideApp () {
   windows.main.hide()
 }
-
-function quitApp (e) {
-  e.preventDefault()
-  windows.main.send('dispatch', 'saveState') /* try to save state on exit */
-  electron.ipcMain.once('savedState', () => electron.app.quit())
-  setTimeout(() => electron.app.quit(), 2000) /* exit after at most 2 secs */
-}