Change the zone allocation api.

runtime/vm/allocation.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/allocation.h"
 
 #include "platform/assert.h"
 #include "vm/isolate.h"
 #include "vm/zone.h"
 
 namespace dart {
 
 ZoneAllocated::~ZoneAllocated() {
   UNREACHABLE();
 }
 
 void* ZoneAllocated::operator new(uword size) {
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   ASSERT(isolate->current_zone() != NULL);
-  return reinterpret_cast<void*>(isolate->current_zone()->Allocate(size));
+  if (size > static_cast<uword>(kIntptrMax)) {
+    FATAL1("ZoneAllocated object has unexpectedly large size %uld", size);
+  }
+  return reinterpret_cast<void*>(isolate->current_zone()->AllocUnsafe(size));
 }
 
 }  // namespace dart