Fixing setTitle on root tree item

Bug: issue 1393
Change-Id: Ie543b8a88ce9c236df3520e400ccfabd91770762

user/src/com/google/gwt/user/client/ui/TreeItem.java

diff --git a/user/src/com/google/gwt/user/client/ui/TreeItem.java b/user/src/com/google/gwt/user/client/ui/TreeItem.java
index b54027e..4749aba 100644
--- a/user/src/com/google/gwt/user/client/ui/TreeItem.java
+++ b/user/src/com/google/gwt/user/client/ui/TreeItem.java
@@ -488,6 +488,16 @@
     return widget;
   }
 
+  @Override
+  public String getTitle() {
+    return contentElem.getTitle();
+  }
+
+  @Override
+  public void setTitle(String title) {
+    contentElem.setTitle(title);
+  }
+
   /**
    * Inserts a child tree item at the specified index containing the specified
    * html.