backout d4bf4c76854e for causing mochitest-other failures

layout/base/FrameLayerBuilder.cpp

@@ -3873,8 +3873,7 @@ FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer,
                              entry->mCommonClipCount);
   }
 
-  if (presContext->GetPaintFlashing() &&
-    aLayer->Manager()->IsWidgetLayerManager()) {
+  if (presContext->GetPaintFlashing()) {
     gfxContextAutoSaveRestore save(aContext);
     if (shouldDrawRectsSeparately) {
       if (aClip == DrawRegionClip::DRAW_SNAPPED) {