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

content/browser/service_worker/service_worker_context_request_handler.cc

Index: content/browser/service_worker/service_worker_context_request_handler.cc
diff --git a/content/browser/service_worker/service_worker_context_request_handler.cc b/content/browser/service_worker/service_worker_context_request_handler.cc
index 4b3535aa5b9eaa18502b95b6ddf4e927b381a90a..553e8126bd83017a872e6d6e52b79e88866ee878 100644
--- a/content/browser/service_worker/service_worker_context_request_handler.cc
+++ b/content/browser/service_worker/service_worker_context_request_handler.cc
@@ -191,7 +191,13 @@ net::URLRequestJob* ServiceWorkerContextRequestHandler::MaybeCreateJobImpl(
   int extra_load_flags = 0;
   base::TimeDelta time_since_last_check =
       base::Time::Now() - registration->last_update_check();
-  if (time_since_last_check > kServiceWorkerScriptMaxCacheAge ||
+  bool should_bypass_cache =
+      (is_main_script && registration->update_via_cache() !=
+                             blink::WebServiceWorkerUpdateViaCache::kAll) ||
+      registration->update_via_cache() ==
+          blink::WebServiceWorkerUpdateViaCache::kNone;

[nhiroki, 2017/08/04 09:24:50]

Would it be possible to move this policy decision to a separate function like
DetermineIfShouldBypassCache() as follows and add a unit test that covers all
possible combinations?

bool DetermineIfShouldBypassCache(
    bool is_main_script,
    blink::WebServiceWorkerUpdateViaCache cache_mode) {
  if (cache_mode == blink::WebServiceWorkerUpdateViaCache::kNone)
    return true;
  if (is_main_script && blink::WebServiceWorkerUpdateViaCache::kImported)
    return true;
  return false;
}

[yuryu, 2017/08/17 07:36:35]

I think it makes sense to extract the part to another method as it is fairly
complex already, but I'm not sure if we can/should test functions with internal
linkage.

+  if (should_bypass_cache ||
+      time_since_last_check > kServiceWorkerScriptMaxCacheAge ||
       version_->force_bypass_cache_for_scripts()) {
     extra_load_flags = net::LOAD_BYPASS_CACHE;
   }