title: GWT FocusPanel setProperty("left",xx") does not work
body: <p>I am implementing "drag" applying "set left".</p>
  
  <p>Here are my code: </p>
  
  <pre><code>scrollPanel.setWidget(focusPanel);//add a focusPanel to the existing scrollPanel
  focusPanel.setWidget(flowPanel); //add a flowPanelto the existing focusPanel
  flowPanel.add(image) // add a image to  the flowPanel
  </code></pre>
  
  <p>scrollPanel.setPixelSize(scrollPanle_width,scrollPanle_height)
  focusPanel.setPixelSize(image_width, image__height)</p>
  
  <p>Enlarge the image, so  image size is larger than scrollPanel size</p>
  
  <p>Try to drag the image to be viewed inside scrollPanel, </p>
  
  <p>(1)Working way</p>
  
  <pre><code>flowPanel.getElement().getStyle().setPropertyPx("left",  offset );
  </code></pre>
  
  <p>When drag, image could be moved.</p>
  
  <p>(2)Not working </p>
  
  <pre><code>focusPanel.getElement().getStyle().setPropertyPx("left",  offset );
  </code></pre>
  
  <p>When drag, image could not be moved.
  Also try this and no luck
      Widget focusPanelWidget = scrollPanel.getWidget();
      focusPanelWidget.getElement().getStyle().setPropertyPx("left",  offset );</p>
  
  <p>So Any one could help to see why "set left" does not work for focusPanel?
  Do appreciate any help!</p>
  
  <p>Many thanks!</p>