Make DOMWrapperWorld::current() return a reference instead of a pointer

Source/bindings/v8/V8WindowShell.h

Index: Source/bindings/v8/V8WindowShell.h
diff --git a/Source/bindings/v8/V8WindowShell.h b/Source/bindings/v8/V8WindowShell.h
index 2ee630975042b0fe208409926d7f19d98ac52534..de6c901894a6b2a3f6a3f0b6c41270978b7f2289 100644
--- a/Source/bindings/v8/V8WindowShell.h
+++ b/Source/bindings/v8/V8WindowShell.h
@@ -55,7 +55,7 @@ class SecurityOrigin;
 // persist between navigations.
 class V8WindowShell {
 public:
-    static PassOwnPtr<V8WindowShell> create(LocalFrame*, PassRefPtr<DOMWrapperWorld>, v8::Isolate*);
+    static PassOwnPtr<V8WindowShell> create(LocalFrame*, DOMWrapperWorld&, v8::Isolate*);
 
     v8::Local<v8::Context> context() const { return m_perContextData ? m_perContextData->context() : v8::Local<v8::Context>(); }
 
@@ -78,7 +78,7 @@ public:
     void clearForNavigation();
     void clearForClose();
 
-    DOMWrapperWorld* world() { return m_world.get(); }
+    DOMWrapperWorld& world() { return *m_world; }
 
 private:
     V8WindowShell(LocalFrame*, PassRefPtr<DOMWrapperWorld>, v8::Isolate*);