Reduce weak callback stack reservation for non-main threads.

third_party/WebKit/Source/platform/heap/ThreadState.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 113 matching lines @@
             s_mainThreadUnderestimatedStackSize = underestimatedStackSize - sizeof(void*);
     }
 
     for (int heapIndex = 0; heapIndex < BlinkGC::LargeObjectHeapIndex; heapIndex++)
         m_heaps[heapIndex] = new NormalPageHeap(this, heapIndex);
     m_heaps[BlinkGC::LargeObjectHeapIndex] = new LargeObjectHeap(this, BlinkGC::LargeObjectHeapIndex);
 
     m_likelyToBePromptlyFreed = adoptArrayPtr(new int[likelyToBePromptlyFreedArraySize]);
     clearHeapAges();
 
-    m_threadLocalWeakCallbackStack = new CallbackStack();
+    // There is little use of weak references and collections off the main thread;
+    // use a much lower initial block reservation.
+    size_t initialBlockSize = isMainThread() ? CallbackStack::kDefaultBlockSize : CallbackStack::kMinimalBlockSize;
+    m_threadLocalWeakCallbackStack = new CallbackStack(initialBlockSize);
 }
 
 ThreadState::~ThreadState()
 {
     ASSERT(checkThread());
     delete m_threadLocalWeakCallbackStack;
     m_threadLocalWeakCallbackStack = nullptr;
     for (int i = 0; i < BlinkGC::NumberOfHeaps; ++i)
         delete m_heaps[i];
 
@@ skipping 1390 matching lines @@
     threadDump->addScalar("dead_count", "objects", totalDeadCount);
     threadDump->addScalar("live_size", "bytes", totalLiveSize);
     threadDump->addScalar("dead_size", "bytes", totalDeadSize);
 
     WebMemoryAllocatorDump* heapsDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(heapsDumpName);
     WebMemoryAllocatorDump* classesDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(classesDumpName);
     BlinkGCMemoryDumpProvider::instance()->currentProcessMemoryDump()->addOwnershipEdge(classesDump->guid(), heapsDump->guid());
 }
 
 } // namespace blink