userportal, webadmin: work around GWT-P memory leak

We encountered a fairly large memory leak in the latest
version of GWT-P. All GWT-P popups have a resize handler
attached to them, but this handler lives at window scope
and never lets go. Therefore, every popup is completely
leaked when closed.

However, luckily, the method in GWT-P that sets up this
handler has a hook/template method for disabling the addition
of the handler:
    if (repositionOnWindowResize()) {
         Window.addResizeHandler(new ResizeHandler() ...

We simply overload repositionOnWindowResize() to always
return false and the leak is worked around.

See: ArcBees/GWTP#823

Change-Id: I4e6d4da68e3f50f5863f4e33e62581b97e36dd2d
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>

frontend/webadmin/modules/gwt-common/src/main/java/org/ovirt/engine/ui/common/view/AbstractPopupView.java

@@ -33,6 +33,16 @@ protected final void initWidget(IsWidget widget) {
         throw new IllegalArgumentException("Use initWidget(PopupPanel) instead of initWidget(Widget)"); //$NON-NLS-1$
     }
 
+    /**
+     * Return false to work around GWT-P memory leak. The resize handler implementation is broken,
+     * so turn it off
+     * See: https://github.com/ArcBees/GWTP/issues/823
+     */
+    @Override
+    protected boolean repositionOnWindowResize() {
+        return false;
+    }
+
     protected void initWidget(T widget) {
         super.initWidget(widget);