PartitionAlloc: Add a lock to Partitions::initialize()

Source/wtf/Partitions.h

 /*
  * 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 81 matching lines @@
         return totalSize;
     }
 
     static void decommitFreeableMemory();
 
     static void reportMemoryUsageHistogram();
 
     static void dumpMemoryStats(PartitionStatsDumper*);
 
 private:
+    static int s_lock;

[tkent, 2015/07/14 00:42:36]

let's give more descriptive name.  e.g. s_initializationLock

     static bool s_initialized;
     static PartitionAllocatorGeneric m_fastMallocAllocator;
     static PartitionAllocatorGeneric m_bufferAllocator;
     static SizeSpecificPartitionAllocator<3328> m_objectModelAllocator;
     static SizeSpecificPartitionAllocator<1024> m_layoutAllocator;
     static HistogramEnumerationFunction m_histogramEnumeration;
 };
 
 } // namespace WTF
 
 #endif // Partitions_h