Window prerequisites for ShelfWindowWatcher panel support.

components/exo/shell_surface.h

Index: components/exo/shell_surface.h
diff --git a/components/exo/shell_surface.h b/components/exo/shell_surface.h
index 511a57cbffbca9a94e54b96981da226680a6334b..d60aab4b76753d62ee72943a44e43b4f299d6d04 100644
--- a/components/exo/shell_surface.h
+++ b/components/exo/shell_surface.h
@@ -124,11 +124,10 @@ class ShellSurface : public SurfaceDelegate,
 
   // Sets the application ID for the window. The application ID identifies the
   // general class of applications to which the window belongs.
-  static void SetApplicationId(aura::Window* window,
-                               std::string* application_id);
+  static void SetApplicationId(aura::Window* window, const std::string& id);
   static const std::string GetApplicationId(aura::Window* window);
 
-  // Set application id for surface.
+  // Set the application ID for the surface.
   void SetApplicationId(const std::string& application_id);
 
   // Start an interactive move of surface.