Revert of Explicit notification and removal of lifecycle observers.

Source/core/workers/WorkerGlobalScope.cpp

Index: Source/core/workers/WorkerGlobalScope.cpp
diff --git a/Source/core/workers/WorkerGlobalScope.cpp b/Source/core/workers/WorkerGlobalScope.cpp
index 0b4146921bf7a3f778860dceddc44005e00f9b4f..1699766d3f6631ec4627747717212073bf0bc3d1 100644
--- a/Source/core/workers/WorkerGlobalScope.cpp
+++ b/Source/core/workers/WorkerGlobalScope.cpp
@@ -93,6 +93,9 @@
 
 WorkerGlobalScope::~WorkerGlobalScope()
 {
+#if !ENABLE(OILPAN)
+    dispose();
+#endif
 }
 
 void WorkerGlobalScope::applyContentSecurityPolicyFromString(const String& policy, ContentSecurityPolicyHeaderType contentSecurityPolicyType)
@@ -193,21 +196,18 @@
 {
     ASSERT(thread()->isCurrentThread());
 
+    // Notify proxy that we are going away. This can free the WorkerThread object, so do not access it after this.
+    thread()->workerReportingProxy().workerGlobalScopeDestroyed();
+
     clearScript();
     clearInspector();
     setClient(0);
 
-    // Observers must not access the context of a disposed WorkerGlobalScope
-    // lacking a thread object.
-    //
-    // Notify them now that the context has been destroyed and explicitly remove
-    // them as observers. If this is delayed until the LifecycleNotifier of the
-    // WorkerGlobalScope is garbage collected and destructed, some observers
-    // may have access to the disposed object (it all depends on the order
-    // the garbage collector finalizes these objects.) Prevent that situation from
-    // arising here.
-    removeAllLifecycleObservers();
-    clearThread();
+    // The thread reference isn't currently cleared, as the execution
+    // context's thread is accessed by GCed lifetime objects when
+    // they're finalized.
+    // FIXME: oilpan: avoid by explicitly removing the WorkerGlobalScope
+    // as an observable context right here.
 }
 
 void WorkerGlobalScope::importScripts(const Vector<String>& urls, ExceptionState& exceptionState)