enable / disable Long Task instrumentation based on presence of LongTask observer

third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h

Index: third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h
diff --git a/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h b/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h
index 467bf8a9832f11fea567feaef9c984128d004a4b..471538be4474ce358fa4ab80d0c07a5adbaae5e7 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h
+++ b/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.h
@@ -29,6 +29,9 @@ public:
     ~InspectorWebPerfAgent();
     DECLARE_VIRTUAL_TRACE();
 
+    void enable();
+    void disable();
+
     void willExecuteScript(ExecutionContext*);
     void didExecuteScript();
 
@@ -40,6 +43,7 @@ public:
     void ReportTaskTime(double startTime, double endTime) override;
 
 private:
+    bool m_enabled;
     Member<InspectedFrames> m_inspectedFrames;
     HeapHashSet<Member<Location>> m_frameContextLocations;
 };