Bug 1291891 - Switch to NS_WARNING for various unimplemented incremental restyle methods. r=emilio

No need to bring the browser down.

layout/base/ServoRestyleManager.cpp

@@ -64,7 +64,7 @@ void
 ServoRestyleManager::PostRebuildAllStyleDataEvent(nsChangeHint aExtraHint,
                                                   nsRestyleHint aRestyleHint)
 {
-  MOZ_CRASH("stylo: ServoRestyleManager::PostRebuildAllStyleDataEvent not implemented");
+  NS_WARNING("stylo: ServoRestyleManager::PostRebuildAllStyleDataEvent not implemented");
 }
 
 void