Add help button to app launcher

ash/shell/app_list.cc

Index: ash/shell/app_list.cc
diff --git a/ash/shell/app_list.cc b/ash/shell/app_list.cc
index 7ee4d388b1cd2f87d90109dd9815ebb403f5697d..82e63d861ac107aa1618568d76ca980d13e0042d 100644
--- a/ash/shell/app_list.cc
+++ b/ash/shell/app_list.cc
@@ -307,6 +307,10 @@ class ExampleAppListViewDelegate : public app_list::AppListViewDelegate {
     // Nothing needs to be done.
   }
 
+  virtual void OpenHelp() OVERRIDE {
+    // Nothing needs to be done.
+  }
+
   virtual void OpenFeedback() OVERRIDE {
     // Nothing needs to be done.
   }