cros: Fix use-after-free in tap visualizer app

|display_id_to_renderer_| has dependency on aura. When used as
a mojo app, |aura_init_| provide aura and should be released
after it.

Bug: None
Change-Id: Ice4410def29166c77ebc8431fd62995c5dbe57f7
Reviewed-on: https://chromium-review.googlesource.com/c/1357082Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612844}

ash/components/tap_visualizer/tap_visualizer_app.h

@@ -56,11 +56,13 @@ class TapVisualizerApp : public service_manager::Service,
 
   service_manager::ServiceBinding service_binding_;
 
+  // Must be released after |display_id_to_renderer_| which indirectly depends
+  // on aura.
+  std::unique_ptr<views::AuraInit> aura_init_;
+
   // Maps display::Display::id() to the renderer for that display.
   std::map<int64_t, std::unique_ptr<TapRenderer>> display_id_to_renderer_;
 
-  std::unique_ptr<views::AuraInit> aura_init_;
-
   DISALLOW_COPY_AND_ASSIGN(TapVisualizerApp);
 };