Report DOM partitionAlloc size to V8 GC.

Source/wtf/PartitionAlloc.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 236 matching lines @@
 // next extent (if there is one) at the very start of a superpage's metadata
 // area.
 struct PartitionSuperPageExtentEntry {
     PartitionRootBase* root;
     char* superPageBase;
     char* superPagesEnd;
     PartitionSuperPageExtentEntry* next;
 };
 
 struct WTF_EXPORT PartitionRootBase {
+    size_t totalSizeOfCommittedPages;
     size_t totalSizeOfSuperPages;
     unsigned numBuckets;
     unsigned maxAllocation;
     bool initialized;
     char* nextSuperPage;
     char* nextPartitionPage;
     char* nextPartitionPageEnd;
     PartitionSuperPageExtentEntry* currentExtent;
     PartitionSuperPageExtentEntry* firstExtent;
     PartitionPage* globalEmptyPageRing[kMaxFreeableSpans];
@@ skipping 395 matching lines @@
 using WTF::partitionAlloc;
 using WTF::partitionFree;
 using WTF::partitionAllocGeneric;
 using WTF::partitionFreeGeneric;
 using WTF::partitionReallocGeneric;
 using WTF::partitionAllocActualSize;
 using WTF::partitionAllocSupportsGetSize;
 using WTF::partitionAllocGetSize;
 
 #endif // WTF_PartitionAlloc_h