Introduce ServiceWorkerHandle for tracking WebServiceWorkerImpl reference

content/browser/service_worker/service_worker_version_unittest.cc

Index: content/browser/service_worker/service_worker_version_unittest.cc
diff --git a/content/browser/service_worker/service_worker_version_unittest.cc b/content/browser/service_worker/service_worker_version_unittest.cc
index 7fe63de43bcaad615fa27ea52382b832d55a784e..63150a365d95e8f06d263e5343c11a021440e73c 100644
--- a/content/browser/service_worker/service_worker_version_unittest.cc
+++ b/content/browser/service_worker/service_worker_version_unittest.cc
@@ -122,9 +122,7 @@ class ServiceWorkerVersionTest : public testing::Test {
   }
 
   virtual void TearDown() OVERRIDE {
-    version_->Shutdown();
     version_ = 0;
-    registration_->Shutdown();
     registration_ = 0;
     helper_.reset();
     context_.reset();