Fix crash in AsyncCallTracker::didEnqueueMutationRecord

Source/core/inspector/AsyncCallTracker.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 292 matching lines @@
         willFireAsyncCall(V8DebuggerAgent::unknownAsyncOperationId);
 }
 
 void AsyncCallTracker::didEnqueueMutationRecord(ExecutionContext* context, MutationObserver* observer)
 {
     ASSERT(context);
     ASSERT(m_debuggerAgent->trackingAsyncCalls());
     ExecutionContextData* data = createContextDataIfNeeded(context);
     if (data->m_mutationObserverCallChains.contains(observer))
         return;
+    Optional<ScriptForbiddenScope::AllowUserAgentScript> allowScripting;
+    if (isMainThread())
+        allowScripting.emplace();
     int operationId = m_debuggerAgent->traceAsyncOperationStarting(enqueueMutationRecordName);
     data->m_mutationObserverCallChains.set(observer, operationId);
 }
 
 void AsyncCallTracker::didClearAllMutationRecords(ExecutionContext* context, MutationObserver* observer)
 {
     ASSERT(context);
     ASSERT(m_debuggerAgent->trackingAsyncCalls());
     if (ExecutionContextData* data = m_executionContextDataMap.get(context))
         data->m_mutationObserverCallChains.remove(observer);
@@ skipping 111 matching lines @@
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_executionContextDataMap);
     visitor->trace(m_debuggerAgent);
     visitor->trace(m_instrumentingAgents);
 #endif
     V8DebuggerAgent::AsyncCallTrackingListener::trace(visitor);
 }
 
 } // namespace blink