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..f477d3ed45b690642cc48aa56f378c75d08df6a8 100644
--- a/content/public/browser/service_worker_context.h
+++ b/content/public/browser/service_worker_context.h
@@ -60,6 +60,15 @@ 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,
+                                        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