Clean up the fix of DevTools crashing in AsyncCallTracker.

Source/core/inspector/AsyncCallTracker.cpp

Index: Source/core/inspector/AsyncCallTracker.cpp
diff --git a/Source/core/inspector/AsyncCallTracker.cpp b/Source/core/inspector/AsyncCallTracker.cpp
index a35e842274a4b2156959358aea1d49d25cbd6471..fdfd8d50095f6ca3c76dacd2dc2e4841b5cc8a04 100644
--- a/Source/core/inspector/AsyncCallTracker.cpp
+++ b/Source/core/inspector/AsyncCallTracker.cpp
@@ -78,13 +78,17 @@ public:
     virtual void contextDestroyed() override

[haraken, 2015/01/13 15:17:48]

Who removes the ExecutionContextData from the observee (i.e., ExecutionContext)?
Or are you intentionally leaving the ExecutionContextData on the observee,
assuming that the ExecutionContext will be destructed soon? (That will work but
sound a bit hacky.)

[aandrey, 2015/01/13 15:39:25]

We could not unobserve from contextDestroyed() callback until your recent patch.
In this patch I assume this invariant is still valid.

The new unobserve() calls dispose() from the parent class which actually removes
the ExecutionContextData from the observee.

     {
         ASSERT(executionContext());
-        // It is possible that resetAsyncCallChains() is already called and thus
-        // this ExecutionContextData is removed from m_executionContextDataMap.
         OwnPtrWillBeRawPtr<ExecutionContextData> self = m_tracker->m_executionContextDataMap.take(executionContext());
-        if (self) {
-            dispose();
-        }
+        ASSERT_UNUSED(self, self == this);
         ContextLifecycleObserver::contextDestroyed();
+        clearLifecycleContext();
+        disposeCallChains();
+    }
+
+    void unobserve()
+    {
+        disposeCallChains();
+        dispose();
     }
 
     int nextAsyncOperationUniqueId()
@@ -112,17 +116,6 @@ public:
         ContextLifecycleObserver::trace(visitor);
     }
 
-    void dispose()
-    {
-        m_timerCallChains.dispose();
-        m_animationFrameCallChains.dispose();
-        m_eventCallChains.dispose();
-        m_xhrCallChains.dispose();
-        m_mutationObserverCallChains.dispose();
-        m_executionContextTaskCallChains.dispose();
-        m_asyncOperationCallChains.dispose();
-    }
-
     RawPtrWillBeMember<AsyncCallTracker> m_tracker;
     HashSet<int> m_intervalTimerIds;
     AsyncCallChainMap<int> m_timerCallChains;
@@ -134,6 +127,17 @@ public:
     AsyncCallChainMap<int> m_asyncOperationCallChains;
 
 private:
+    void disposeCallChains()
+    {
+        m_timerCallChains.dispose();
+        m_animationFrameCallChains.dispose();
+        m_eventCallChains.dispose();
+        m_xhrCallChains.dispose();
+        m_mutationObserverCallChains.dispose();
+        m_executionContextTaskCallChains.dispose();
+        m_asyncOperationCallChains.dispose();
+    }
+
     int m_circularSequentialId;
 };
 
@@ -166,7 +170,7 @@ void AsyncCallTracker::asyncCallTrackingStateChanged(bool tracking)
 void AsyncCallTracker::resetAsyncCallChains()
 {
     for (auto& it : m_executionContextDataMap)
-        it.value->dispose();
+        it.value->unobserve();
     m_executionContextDataMap.clear();
 }