Fix an edge case where early disconnect() can omit delivering of observation. crbug/607324

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

Index: third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
diff --git a/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp b/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
index fdef12967f1b4fa32c4c27179c0accc677f36897..920a8d5ce3e84a6acd3a792946ff2c0fbc6d8802 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
@@ -57,9 +57,10 @@ void PerformanceObserver::observe(const PerformanceObserverInit& observerInit, E
 
 void PerformanceObserver::disconnect()
 {
-    m_performanceEntries.clear();
     if (m_performance)
         m_performance->unregisterPerformanceObserver(*this);
+
+    m_performanceEntries.clear();
     m_isRegistered = false;
 }