title: Disclosure panel header widget client bundle,@sprite is not working
body: <p>I am having <a href="http://google-web-toolkit.googlecode.com/svn/javadoc/2.0/com/google/gwt/user/client/ui/DisclosurePanel.html" rel="nofollow">DisclosurePanel</a>, as header content i have <a href="http://google-web-toolkit.googlecode.com/svn/javadoc/2.0/com/google/gwt/user/client/ui/HorizontalPanel.html" rel="nofollow">HorizontalPanel</a> which is applied style, these styles is having background image, which uses ClientBundle with @sprite.
  But issue is the style is not applying for the header widget (Horizontal Panel)</p>
  
  <p>here my code goes</p>
  
  <p><strong>Entry class</strong></p>
  
  <pre><code>public class Test implements EntryPoint {
  
      /**
       * This is the entry point method.
       */
      public void onModuleLoad() {
          TestClientBundle.INSTANCE.testCsss().ensureInjected();
          DisclosurePanel dp = new DisclosurePanel();
          HorizontalPanel hp = new HorizontalPanel();
          dp.setStyleName("blue");
          Label l = new Label("testing the DP with IMG-CSS bundle");
          hp.add(l);
          dp.setHeader(hp);
          dp.setContent(new Label("Body"));
          RootPanel.get().add(dp);
      }
  }
  </code></pre>
  
  <p><strong>ClientBundle interface</strong> </p>
  
  <pre><code>public interface TestClientBundle extends ClientBundle {
  
      TestClientBundle INSTANCE = GWT.create(TestClientBundle.class);
  
      @Source("blue.jpg")
      public ImageResource blue();
  
      @Source("test.css")
      public CssResource testCsss();
  }
  </code></pre>
  
  <p><strong>Css File</strong></p>
  
  <pre><code>@external .blue;
  @sprite .blue {
      gwt-image: 'blue';
      cursor: pointer;
      text-decoration: none;
  }
  </code></pre>
  
  <p>Is it known issue in GWT or my code is wrong?</p>