Replacing the 'return 0;' statements with 'return nullptr;'

public/platform/WebServiceWorker.h

Index: public/platform/WebServiceWorker.h
diff --git a/public/platform/WebServiceWorker.h b/public/platform/WebServiceWorker.h
index a972ffa0976f415b1e2c5968c1bb1950666f0588..44b307d4848f59efd1f3d276589759bb22f0cb74 100644
--- a/public/platform/WebServiceWorker.h
+++ b/public/platform/WebServiceWorker.h
@@ -52,7 +52,7 @@ public:
     // ownership to the callee, and the proxy's lifetime is same as that of
     // WebServiceWorker.
     virtual void setProxy(WebServiceWorkerProxy*) { }
-    virtual WebServiceWorkerProxy* proxy() { return 0; }
+    virtual WebServiceWorkerProxy* proxy() { return nullptr; }
 
     virtual WebURL url() const { return WebURL(); }
     virtual WebServiceWorkerState state() const { return WebServiceWorkerStateUnknown; }