Add ref count to service workers for extension API.

content/public/browser/service_worker_context.h

Index: content/public/browser/service_worker_context.h
diff --git a/content/public/browser/service_worker_context.h b/content/public/browser/service_worker_context.h
index 47f355c734ae46b1a5e17b04968f898a526901c0..e8bb16a33e04d14c5937d4301c25739fa6b84f2e 100644
--- a/content/public/browser/service_worker_context.h
+++ b/content/public/browser/service_worker_context.h
@@ -33,6 +33,9 @@ class ServiceWorkerContext {
   typedef base::Callback<void(bool has_service_worker)>
       CheckHasServiceWorkerCallback;
 
+  typedef base::Callback<void(size_t external_request_count)>
+      GetPendingExternalRequestCountCallback;
+
   // Registers the header name which should not be passed to the ServiceWorker.
   // Must be called from the IO thread.
   CONTENT_EXPORT static void AddExcludedHeadersForFetchEvent(
@@ -60,6 +63,15 @@ class ServiceWorkerContext {
                                      const GURL& script_url,
                                      const ResultCallback& callback) = 0;
 
+  // Ref count mechanism for embedder to increment/decrement activity count of a
+  // service worker.
+  // Must be called from the IO thread. Returns whether or not changing the
+  // activity count succeeded.
+  virtual bool IncrementPendingActivity(int64_t service_worker_version_id,

[Devlin, 2016/10/07 15:13:22]

Drive-by: Since these are all associated with a specific uuid, it seems like
maybe this should be "AddPendingActivitiy" and "RemovePendingActivity" (and
maybe make activity_uuid, or replace activity with request in method names?). 
Increment/Decrement makes it sound like there's a separate counter.

But this is really a content/ OWNERS choice, so I'm happy either way - just my
$0.02.

[lazyboy, 2016/10/07 18:50:10]

OK, will do before sending out to content/public review.

[michaeln, 2016/10/07 20:10:30]

i was thinking a rename would be good too, maybe match the naming in the impl

  StartingExternalRequest()
  FinishedExternalRequest()

and later, when needed

  ExtendingExternalRequest() to keep it alive for longer

[lazyboy, 2016/10/07 21:28:41]

Changed the names to reflect this is request instead of activity.

+                                        const std::string& request_uuid) = 0;
+  virtual bool DecrementPendingActivity(int64_t service_worker_version_id,
+                                        const std::string& request_uuid) = 0;
+
   // Equivalent to calling navigator.serviceWorker.unregister(pattern) from a
   // renderer, except that |pattern| is an absolute URL instead of relative to
   // some current origin.  |callback| is passed true when the JS promise is
@@ -96,6 +108,12 @@ class ServiceWorkerContext {
       const GURL& other_url,
       const CheckHasServiceWorkerCallback& callback) = 0;
 
+  // Returns the pending activity count for the worker with the specified
+  // |origin| via |callback|.
+  virtual void GetPendingExternalRequestCountForTest(

[michaeln, 2016/10/07 20:10:30]

and this could be something like CountExternalRequestsFrTest

[lazyboy, 2016/10/07 21:28:41]

Done.

+      const GURL& origin,
+      const GetPendingExternalRequestCountCallback& callback) = 0;
+
   // Stops all running workers on the given |origin|.
   //
   // This function can be called from any thread.