Bug 1237982 - Force perspective layers to always be active. r=thinker

--HG--
extra : rebase_source : c831e2bc3413a0dfca34cb5e8f148ac1b06b40b8

layout/base/nsDisplayList.cpp

@@ -6182,7 +6182,7 @@ nsDisplayPerspective::GetLayerState(nsDisplayListBuilder* aBuilder,
                                     LayerManager* aManager,
                                     const ContainerLayerParameters& aParameters)
 {
-  return LAYER_ACTIVE;
+  return LAYER_ACTIVE_FORCE;
 }
 
 nsDisplayItemGeometry*