Explicitly dispose of async call chains.

Source/core/inspector/InspectorDebuggerAgent.cpp

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 117 matching lines @@
     , m_recursionLevelForStepFrame(0)
     , m_skipAllPauses(false)
     , m_skipContentScripts(false)
     , m_cachedSkipStackGeneration(0)
     , m_promiseTracker(PromiseTracker::create())
     , m_maxAsyncCallStackDepth(0)
     , m_currentAsyncCallChain(nullptr)
     , m_nestedAsyncCallCount(0)
     , m_performingAsyncStepIn(false)
 {
-    m_v8AsyncCallTracker = adoptPtrWillBeNoop(new V8AsyncCallTracker(this));
+    m_v8AsyncCallTracker = V8AsyncCallTracker::create(this);
 }
 
 InspectorDebuggerAgent::~InspectorDebuggerAgent()
 {
 #if !ENABLE(OILPAN)
     ASSERT(!m_instrumentingAgents->inspectorDebuggerAgent());
 #endif
 }
 
 void InspectorDebuggerAgent::init()
@@ skipping 1415 matching lines @@
     visitor->trace(m_v8AsyncCallTracker);
     visitor->trace(m_promiseTracker);
     visitor->trace(m_asyncOperationsForStepInto);
     visitor->trace(m_currentAsyncCallChain);
     visitor->trace(m_asyncCallTrackingListeners);
 #endif
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink