Oilpan: fix build after r187699.

Source/core/inspector/AsyncCallStackTracker.cpp

Index: Source/core/inspector/AsyncCallStackTracker.cpp
diff --git a/Source/core/inspector/AsyncCallStackTracker.cpp b/Source/core/inspector/AsyncCallStackTracker.cpp
index e80885b0cd834f3a0ef2e279d39913a621e6ef54..b2ff070507d7978f5685b48902c032652ccdd6e1 100644
--- a/Source/core/inspector/AsyncCallStackTracker.cpp
+++ b/Source/core/inspector/AsyncCallStackTracker.cpp
@@ -149,7 +149,9 @@ AsyncCallStackTracker::AsyncCallStackTracker(InspectorDebuggerAgent* debuggerAge
     m_debuggerAgent->addAsyncCallTrackingListener(this);
 }
 
-DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(AsyncCallStackTracker);
+AsyncCallStackTracker::~AsyncCallStackTracker()
+{
+}
 
 void AsyncCallStackTracker::asyncCallTrackingStateChanged(bool tracking)
 {
@@ -440,7 +442,10 @@ void AsyncCallStackTracker::trace(Visitor* visitor)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_executionContextDataMap);
+    visitor->trace(m_debuggerAgent);
+    visitor->trace(m_instrumentingAgents);
 #endif
+    InspectorDebuggerAgent::AsyncCallTrackingListener::trace(visitor);
 }
 
 } // namespace blink