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

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 f48991b039240fe19ca480552461236ebabc84d6..1c5fb3d84657a04bc2e19f2a783c6f78b93ea257 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceBase.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceBase.cpp
@@ -352,6 +352,12 @@ void PerformanceBase::registerPerformanceObserver(PerformanceObserver& observer)
 
 void PerformanceBase::unregisterPerformanceObserver(PerformanceObserver& oldObserver)
 {
+    ASSERT(isMainThread());
+    // Deliver any pending observations on this observer before unregistering.
+    if (m_activeObservers.contains(&oldObserver) && !oldObserver.shouldBeSuspended()) {
+        oldObserver.deliver();
+        m_activeObservers.remove(&oldObserver);
+    }
     m_observers.remove(&oldObserver);
     updatePerformanceObserverFilterOptions();
 }