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

content/browser/service_worker/service_worker_context_core.h

Index: content/browser/service_worker/service_worker_context_core.h
diff --git a/content/browser/service_worker/service_worker_context_core.h b/content/browser/service_worker/service_worker_context_core.h
index bb1fc8993cc8fca8c8472648306c06ccd72031bb..6dff23a1b9a6aed9355d7c40a4f95dea25586088 100644
--- a/content/browser/service_worker/service_worker_context_core.h
+++ b/content/browser/service_worker/service_worker_context_core.h
@@ -196,6 +196,7 @@ class CONTENT_EXPORT ServiceWorkerContextCore
   // Non-null |provider_host| must be given if this is called from a document.
   void RegisterServiceWorker(const GURL& pattern,
                              const GURL& script_url,
+                             bool use_cache,

[nhiroki, 2017/03/24 00:33:42]

Enum would be better than boolean for readability[1]. We could define it in
service_worker_types.h, for example, as follows:

  struct CONTENT_EXPORT ServiceWorkerRegistrationOptions {
    enum class UseCache { DontUse, Use };
    // ...
    UseCache use_cache;
  };

[1] "Consider changing the function signature to replace a bool argument with an
enum argument. This will make the argument values self-describing."
https://google.github.io/styleguide/cppguide.html#Implementation_Comments

[yuryu, 2017/03/28 05:08:56]

Done.

                              ServiceWorkerProviderHost* provider_host,
                              const RegistrationCallback& callback);
   void UnregisterServiceWorker(const GURL& pattern,