Remove TLS access for current Zone.

src/zone-inl.h

Index: src/zone-inl.h
diff --git a/src/zone-inl.h b/src/zone-inl.h
index b484208aea349357584b6b6e85185f424defb18d..d75e297af18ee78ff6729a4998c0b6a52fc7dc86 100644
--- a/src/zone-inl.h
+++ b/src/zone-inl.h
@@ -94,29 +94,13 @@ ZoneSplayTree<Config>::~ZoneSplayTree() {
 }
 
 
-// TODO(isolates): for performance reasons, this should be replaced with a new
-//                 operator that takes the zone in which the object should be
-//                 allocated.
-void* ZoneObject::operator new(size_t size) {
-  return ZONE->New(static_cast<int>(size));
-}
-
 void* ZoneObject::operator new(size_t size, Zone* zone) {
   return zone->New(static_cast<int>(size));
 }
 
 inline void* ZoneAllocationPolicy::New(size_t size) {
-  if (zone_) {
-    return zone_->New(size);
-  } else {
-    return ZONE->New(size);
-  }
-}
-
-
-template <typename T>
-void* ZoneList<T>::operator new(size_t size) {
-  return ZONE->New(static_cast<int>(size));
+  ASSERT(zone_);
+  return zone_->New(size);
 }