DevTools: Async call stacks for FileSystem API part 2.

Source/core/inspector/InspectorDebuggerAgent.cpp

Index: Source/core/inspector/InspectorDebuggerAgent.cpp
diff --git a/Source/core/inspector/InspectorDebuggerAgent.cpp b/Source/core/inspector/InspectorDebuggerAgent.cpp
index 4eeeba1cadc5a51039ae56c0c637f0a13aaa64d0..5960060646724301d871a63932bab61b6db85302 100644
--- a/Source/core/inspector/InspectorDebuggerAgent.cpp
+++ b/Source/core/inspector/InspectorDebuggerAgent.cpp
@@ -834,11 +834,13 @@ void InspectorDebuggerAgent::didPerformExecutionContextTask()
         m_asyncCallStackTracker.didFireAsyncCall();
 }
 
-int InspectorDebuggerAgent::traceAsyncOperationStarting(ExecutionContext* context, const String& operationName)
+int InspectorDebuggerAgent::traceAsyncOperationStarting(ExecutionContext* context, const String& operationName, int prevOperationId)
 {
-    if (m_asyncCallStackTracker.isEnabled())
-        return m_asyncCallStackTracker.traceAsyncOperationStarting(context, operationName, scriptDebugServer().currentCallFramesForAsyncStack());
-    return 0;
+    if (!m_asyncCallStackTracker.isEnabled())
+        return 0;
+    if (prevOperationId)
+        m_asyncCallStackTracker.traceAsyncOperationCompleted(context, prevOperationId);
+    return m_asyncCallStackTracker.traceAsyncOperationStarting(context, operationName, scriptDebugServer().currentCallFramesForAsyncStack());
 }
 
 void InspectorDebuggerAgent::traceAsyncOperationCompleted(ExecutionContext* context, int operationId)