Add VaadinSession getter to VaadinService (#9402)

server/src/com/vaadin/server/AbstractVaadinService.java

     public AddonContext getAddonContext() {
         return addonContext;
     }
+
+    @Override
+    public VaadinSession getVaadinSession(WrappedRequest request) {
+        return (VaadinSession) request.getAttribute(VaadinSession.class
+                .getName());
+    }
+
 }

server/src/com/vaadin/server/VaadinPortlet.java

                     return;
                 }
                 VaadinSession.setCurrent(application);
+                request.setAttribute(VaadinSession.class.getName(), application);
 
                 /*
                  * Get or create an application context and an application

server/src/com/vaadin/server/VaadinService.java

      *         base directory.
      */
     public File getBaseDirectory();
+
+    /**
+     * Gets the Vaadin session associated with this request.
+     * 
+     * @param request
+     *            the request to get a vaadin session for.
+     * 
+     * @see VaadinSession
+     * 
+     * @return the vaadin session for the request, or <code>null</code> if no
+     *         session is found and this is a request for which a new session
+     *         shouldn't be created.
+     */
+    public VaadinSession getVaadinSession(WrappedRequest request);
 }

server/src/com/vaadin/server/VaadinServlet.java

             if (application == null) {
                 return;
             }
+            request.setAttribute(VaadinSession.class.getName(), application);
             VaadinSession.setCurrent(application);
 
             /*