Add simple VM test for precompiled code.

runtime/vm/megamorphic_cache_table.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/megamorphic_cache_table.h"
 
 #include <stdlib.h>
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/stub_code.h"
@@ skipping 70 matching lines @@
 }
 
 
 void MegamorphicCacheTable::PrintSizes(Isolate* isolate) {
   StackZone zone(Thread::Current());
   intptr_t size = 0;
   MegamorphicCache& cache = MegamorphicCache::Handle();
   Array& buckets = Array::Handle();
   const GrowableObjectArray& table = GrowableObjectArray::Handle(
       isolate->object_store()->megamorphic_cache_table());
+  if (table.IsNull()) return;
   for (intptr_t i = 0; i < table.Length(); i += kEntrySize) {
     cache ^= table.At(i + kEntryCacheOffset);
     buckets = cache.buckets();
     size += MegamorphicCache::InstanceSize();
     size += Array::InstanceSize(buckets.Length());
   }
   OS::Print("%" Pd " megamorphic caches using %" Pd "KB.\n",
             table.Length() / kEntrySize, size / 1024);
 }
 
 }  // namespace dart