Explicitly dispose of async call chains.

Source/core/inspector/AsyncCallChainMap.h

Index: Source/core/inspector/AsyncCallChainMap.h
diff --git a/Source/core/inspector/AsyncCallChainMap.h b/Source/core/inspector/AsyncCallChainMap.h
index 0e992eae45d7ee5baf64d2ad9f34adc350560dc2..ba7e98c0bc704fa032cc1ee3dd156549f1e48efe 100644
--- a/Source/core/inspector/AsyncCallChainMap.h
+++ b/Source/core/inspector/AsyncCallChainMap.h
@@ -26,10 +26,17 @@ public:
 
     ~AsyncCallChainMap()
     {
-        // Verify that this object has been explicitly cleared already.
-        ASSERT(!m_debuggerAgent);
+        // Verify that this object has been explicitly disposed.
+        ASSERT(hasBeenDisposed());
     }
 
+#if ENABLE(ASSERT)
+    bool hasBeenDisposed() const
+    {
+        return !m_debuggerAgent;
+    }
+#endif
+
     void dispose()
     {
         clear();