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

third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerUpdateViaCache.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WebServiceWorkerUpdateViaCache_h
+#define WebServiceWorkerUpdateViaCache_h
+
+namespace blink {
+
+enum class WebServiceWorkerUpdateViaCache {
+  kUnknown,
+  kImports,
+  kAll,
+  kNone,
+  kLast = kNone,
+};
+
+}  // namespace blink
+
+#endif  // WebServiceWorkerUpdateViaCache_h