service worker: Tweak some documentation.

content/browser/service_worker/embedded_worker_registry.cc

Index: content/browser/service_worker/embedded_worker_registry.cc
diff --git a/content/browser/service_worker/embedded_worker_registry.cc b/content/browser/service_worker/embedded_worker_registry.cc
index f0031c5ec9b0493c4c612d38daf488a92ad9f401..dd28900a60137ea85ec9bfd4058a2eb08280639c 100644
--- a/content/browser/service_worker/embedded_worker_registry.cc
+++ b/content/browser/service_worker/embedded_worker_registry.cc
@@ -256,12 +256,15 @@ ServiceWorkerStatusCode EmbeddedWorkerRegistry::SendStartWorker(
   DCHECK(ContainsKey(process_sender_map_, process_id));
 
   int embedded_worker_id = params->embedded_worker_id;
+#ifndef NDEBUG

[nhiroki, 2016/07/19 03:37:53]

"#if DCHECK_IS_ON()" would be better for DCHECK_ALWAYS_ON

[falken, 2016/07/22 01:34:47]

Acknowledged.

+  // Assert the embedded worker's process id is |process_id|.
   WorkerInstanceMap::iterator found = worker_map_.find(embedded_worker_id);
   DCHECK(found != worker_map_.end());
   DCHECK_EQ(found->second->process_id(), process_id);

[nhiroki, 2016/07/19 03:37:53]

Optional: I'd prefer not to have macros in a production code as much as possible
in terms of readability. With following code, we could avoid them:

DCHECK(GetWorker(embedded_worker_id));
DCHECK_EQ(GetWorker(embedded_worker_id)->process_id(), process_id);

[falken, 2016/07/22 01:34:47]

Much better, done.

-
+  // Assert the embedded worker is not in the map for starting/running workers.
   DCHECK(!ContainsKey(worker_process_map_, process_id) ||
          worker_process_map_[process_id].count(embedded_worker_id) == 0);

[nhiroki, 2016/07/19 03:37:53]

Optional: "!ContainsKey(worker_process_map_[process_id], embedded_worker_id)"
would be consistent with the former expression.

[falken, 2016/07/22 01:34:47]

Huh yea. Not sure why I used count in the first place.

+#endif  // NDEBUG
 
   ServiceWorkerStatusCode status =
       Send(process_id, new EmbeddedWorkerMsg_StartWorker(*params));