PartitionAlloc: improve how statistics appear in chrome://tracing.

Source/wtf/PartitionAlloc.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 1061 matching lines @@
         return;
 
     memset(statsOut, '\0', sizeof(*statsOut));
     statsOut->isValid = true;
     statsOut->isDirectMap = false;
     statsOut->numFullPages = static_cast<size_t>(bucket->numFullPages);
     statsOut->bucketSlotSize = bucket->slotSize;
     uint16_t bucketNumSlots = partitionBucketSlots(bucket);
     size_t bucketUsefulStorage = statsOut->bucketSlotSize * bucketNumSlots;
     statsOut->allocatedPageSize = partitionBucketBytes(bucket);
-    statsOut->pageWasteSize = statsOut->allocatedPageSize - bucketUsefulStorage;
     statsOut->activeBytes = bucket->numFullPages * bucketUsefulStorage;
     statsOut->residentBytes = bucket->numFullPages * statsOut->allocatedPageSize;
 
     for (const PartitionPage* page = bucket->emptyPagesHead; page; page = page->nextPage) {
         // Currently, only decommitted pages appear in the empty pages list.
         // This may change.
         ASSERT(page != &PartitionRootGeneric::gSeedPage);
         ASSERT(!page->freelistHead);
         ASSERT(!page->numAllocatedSlots);
         ASSERT(!page->numUnprovisionedSlots);
@@ skipping 72 matching lines @@
     // partitionsDumpBucketStats is called after collecting stats because it
     // can use PartitionAlloc to allocate and this can affect the statistics.
     for (size_t i = 0; i < partitionNumBuckets; ++i) {
         if (memoryStats[i].isValid)
             partitionStatsDumper->partitionsDumpBucketStats(partitionName, &memoryStats[i]);
     }
 }
 
 } // namespace WTF