Revert "QWidget: Don't re-use backing store on Android"

This reverts commit 4e9eb6bd6f965fdc56b22595d407a489e9c272c1.

Reason for revert: Fixed by 177348f90e1857df1889c73f33a07c5b5e4d29f1

Change-Id: I1c7502c5632c1f38af0c02a2a404b93d44b57776
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/android/qandroidplatformscreen.cpp

@@ -172,7 +172,6 @@ bool QAndroidPlatformScreen::event(QEvent *event)
 
 void QAndroidPlatformScreen::addWindow(QAndroidPlatformWindow *window)
 {
-    Q_ASSERT(window->backingStore());
     if (window->parent() && window->isRaster())
         return;
 

src/widgets/kernel/qwidget.cpp

@@ -1329,13 +1329,7 @@ void QWidgetPrivate::create()
     }
 #endif
 
-    // Android doesn't allow to re-use the backing store.
-    // => force creation of a new one.
-#ifdef Q_OS_ANDROID
-    QBackingStore *store = nullptr;
-#else
     QBackingStore *store = q->backingStore();
-#endif
     usesRhiFlush = false;
 
     if (!store) {