Simplify LifecycleNotifier and Observer.

third_party/WebKit/Source/platform/LifecycleObserver.h

Index: third_party/WebKit/Source/platform/LifecycleObserver.h
diff --git a/third_party/WebKit/Source/platform/LifecycleObserver.h b/third_party/WebKit/Source/platform/LifecycleObserver.h
index 09a9b3dc4d5b07b5309e79996c84a44b63697317..93a364a2ed9bea2ac960d20ad6478d7508b446bc 100644
--- a/third_party/WebKit/Source/platform/LifecycleObserver.h
+++ b/third_party/WebKit/Source/platform/LifecycleObserver.h
@@ -28,7 +28,6 @@
 #define LifecycleObserver_h
 
 #include "platform/heap/Handle.h"
-#include "wtf/Assertions.h"
 
 namespace blink {
 
@@ -37,13 +36,6 @@ class LifecycleObserver : public GarbageCollectedMixin {
 public:
     using Context = T;
 
-#if !ENABLE(OILPAN)
-    virtual ~LifecycleObserver()
-    {
-        clearContext();
-    }
-#endif
-
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         visitor->trace(m_lifecycleContext);
@@ -52,7 +44,6 @@ public:
     virtual void contextDestroyed() { }
 
     Context* lifecycleContext() const { return m_lifecycleContext; }
-    void clearLifecycleContext() { m_lifecycleContext = nullptr; }
 
 protected:
     explicit LifecycleObserver(Context* context)