[WIP]Oilpan: checking for nearly-dead observers.

Source/core/frame/LocalFrameLifecycleNotifier.cpp

Index: Source/core/frame/LocalFrameLifecycleNotifier.cpp
diff --git a/Source/core/frame/LocalFrameLifecycleNotifier.cpp b/Source/core/frame/LocalFrameLifecycleNotifier.cpp
index 434cf8bc2c36ffdc0ddd766b23b124726e87aeca..7208ca3ca180c9245e92acf860ef600c060b17c5 100644
--- a/Source/core/frame/LocalFrameLifecycleNotifier.cpp
+++ b/Source/core/frame/LocalFrameLifecycleNotifier.cpp
@@ -12,8 +12,13 @@ namespace blink {
 void LocalFrameLifecycleNotifier::notifyWillDetachFrameHost()
 {
     TemporaryChange<IterationType> scope(m_iterating, IteratingOverAll);
-    for (LocalFrameLifecycleObserver* observer : m_observers)
+    for (LocalFrameLifecycleObserver* observer : m_observers) {
+#if !ENABLE(OILPAN)
+        if (!isObserverAlive(observer))
+            continue;
+#endif
         observer->willDetachFrameHost();
+    }
 }
 
 } // namespace blink