Show the input switching shortcut in keyboard hints

shell/plugins/bar/widgets/KeyboardLayoutModel.js

@@ -120,7 +120,7 @@ function inputLabel(state, fallback) {
 function inputTooltip(state, layout, multipleLayouts) {
   if (!state || !state.methods || state.methods.length < 2)
     return layout + (multipleLayouts ? "" : "\nClick to set up an input language")
-  var text = state.name + "\nClick to switch input language"
+  var text = state.name + "\nClick to switch input language\nCtrl + Shift + Space to toggle input"
   if (state.methods.indexOf("mozc") !== -1)
     text += "\nJapanese: type a word, then Space twice for character choices"
   if (multipleLayouts) text += "\nRight-click to switch keyboard layout"