#7895 Provide ThreadLocal for the current Root

src/com/vaadin/Application.java

@@ -1476,6 +1476,7 @@ public class Application implements Terminal.ErrorListener, Serializable {
             }
         }
 
+        Root.setCurrentRoot(root);
         return root;
     }
 

src/com/vaadin/terminal/gwt/server/AbstractApplicationPortlet.java

@@ -531,6 +531,7 @@ public abstract class AbstractApplicationPortlet extends GenericPortlet
 
                         }
                     } finally {
+                        Root.setCurrentRoot(null);
                         Application.setCurrentApplication(null);
                     }
                 }

src/com/vaadin/terminal/gwt/server/AbstractApplicationServlet.java

@@ -577,6 +577,7 @@ public abstract class AbstractApplicationServlet extends HttpServlet implements
                                 .onRequestEnd(request, response);
                     }
                 } finally {
+                    Root.setCurrentRoot(null);
                     Application.setCurrentApplication(null);
                 }
 

src/com/vaadin/ui/Root.java

@@ -45,6 +45,8 @@ public class Root extends AbstractComponentContainer {
      */
     private Component scrollIntoView;
 
+    private static final ThreadLocal<Root> currentRoot = new ThreadLocal<Root>();
+
     public Root(RootLayout rootLayout) {
         this.rootLayout = rootLayout;
         addComponent(rootLayout);
@@ -446,4 +448,12 @@ public class Root extends AbstractComponentContainer {
     public void init(WrappedRequest request) {
         getRootLayout().init(request);
     }
+
+    public static void setCurrentRoot(Root root) {
+        currentRoot.set(root);
+    }
+
+    public static Root getCurrentRoot() {
+        return currentRoot.get();
+    }
 }