POC for InspectorInstrumentation adding InspectorWebPerfAgent

third_party/WebKit/Source/core/timing/PerformanceBase.cpp

Index: third_party/WebKit/Source/core/timing/PerformanceBase.cpp
diff --git a/third_party/WebKit/Source/core/timing/PerformanceBase.cpp b/third_party/WebKit/Source/core/timing/PerformanceBase.cpp
index 2ebfe14288d3c697beb95b292b619a925edd2f0c..fce966d9f07eb32e0b25b55ee0e87b4a143e260a 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceBase.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceBase.cpp
@@ -58,6 +58,7 @@ PerformanceBase::PerformanceBase(double timeOrigin)
     , m_userTiming(nullptr)
     , m_observerFilterOptions(PerformanceEntry::Invalid)
     , m_deliverObservationsTimer(this, &PerformanceBase::deliverObservationsTimerFired)
+    , m_inspectorInstrumentationEnabled(false)
 {
 }
 
@@ -75,6 +76,10 @@ PerformanceTiming* PerformanceBase::timing() const
     return nullptr;
 }
 
+void PerformanceBase::enableInspectorInstrumentation() const
+{
+}
+
 PerformanceEntryVector PerformanceBase::getEntries() const
 {
     PerformanceEntryVector entries;
@@ -356,6 +361,16 @@ void PerformanceBase::registerPerformanceObserver(PerformanceObserver& observer)
 {
     m_observerFilterOptions |= observer.filterOptions();
     m_observers.add(&observer);
+
+    // If this is the first long task observer then enable tracking of LongTaskTiming.
+    if (!m_inspectorInstrumentationEnabled
+        && hasObserverFor(PerformanceEntry::Mark)) { // PerformanceEntry::LongTask
+        fprintf(stderr, "\n^^^On observe(): enableInspectorInstrumentation");
+        enableInspectorInstrumentation();
+        m_inspectorInstrumentationEnabled = true;
+    } else {
+        fprintf(stderr, "\n^^^On observe(): NOT enableInspectorInstrumentation");
+    }
 }
 
 void PerformanceBase::unregisterPerformanceObserver(PerformanceObserver& oldObserver)
@@ -368,6 +383,11 @@ void PerformanceBase::unregisterPerformanceObserver(PerformanceObserver& oldObse
     }
     m_observers.remove(&oldObserver);
     updatePerformanceObserverFilterOptions();
+
+    if (m_inspectorInstrumentationEnabled
+        && !hasObserverFor(PerformanceEntry::Mark)) {  // PerformanceEntry::LongTask
+        //disableInspectorInstrumentation();
+    }
 }
 
 void PerformanceBase::updatePerformanceObserverFilterOptions()