Use the partition allocator and run the test in debug too.

Source/core/platform/Partitions.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 26 matching lines @@
 
 PartitionRoot Partitions::m_objectModelRoot;
 
 void Partitions::init()
 {
     partitionAllocInit(&m_objectModelRoot);
 }
 
 void Partitions::shutdown()
 {
-    partitionAllocShutdown(&m_objectModelRoot);
+    // We could ASSERT here for a memory leak within the partition, but it leads
+    // to very hard to diagnose ASSERTs, so it's best to leave leak checking for
+    // the valgrind and heapcheck bots, which run without partitions.
+    (void) partitionAllocShutdown(&m_objectModelRoot);
 }
 #endif
 
 } // namespace WebCore