Implement updateViaCache flag and no-cache by default for main service worker scripts

content/browser/service_worker/service_worker_context_unittest.cc

Index: content/browser/service_worker/service_worker_context_unittest.cc
diff --git a/content/browser/service_worker/service_worker_context_unittest.cc b/content/browser/service_worker/service_worker_context_unittest.cc
index e11bbdc43526bb1568ab0a9b869022a67ac1eb4b..ec2e8e2b90c40935e1bdef700285abc29ab0425a 100644
--- a/content/browser/service_worker/service_worker_context_unittest.cc
+++ b/content/browser/service_worker/service_worker_context_unittest.cc
@@ -79,6 +79,9 @@ void ExpectRegisteredWorkers(
   } else {
     EXPECT_FALSE(registration->active_version());
   }
+
+  EXPECT_EQ(blink::WebServiceWorkerUpdateViaCache::kImports,
+            registration->update_via_cache());
 }
 
 class RejectInstallTestHelper : public EmbeddedWorkerTestHelper {