[WIP] Speculatively launch Service Workers on mouse/touch events.

content/browser/service_worker/service_worker_version.h

Index: content/browser/service_worker/service_worker_version.h
diff --git a/content/browser/service_worker/service_worker_version.h b/content/browser/service_worker/service_worker_version.h
index 9b88f791b286971ad5e1ad1853fa8260df2dfe62..dab02f6caf1c039bfe3595d11b7ed3cf0e611d82 100644
--- a/content/browser/service_worker/service_worker_version.h
+++ b/content/browser/service_worker/service_worker_version.h
@@ -603,6 +603,10 @@ class CONTENT_EXPORT ServiceWorkerVersion
   // event ended).
   void OnBeginEvent();
 
+  // Resets |start_worker_first_purpose_| and fires and clears all start
+  // callbacks.
+  void RunStartCallbacks(ServiceWorkerStatusCode status);
+
   const int64_t version_id_;
   const int64_t registration_id_;
   const GURL script_url_;
@@ -679,6 +683,10 @@ class CONTENT_EXPORT ServiceWorkerVersion
 
   bool stop_when_devtools_detached_ = false;
 
+  // It is used to keep the first purpose of starting the worker for UMA.
+  // Cleared when |start_callbacks_| are executed in RunStartCallbacks().
+  std::unique_ptr<ServiceWorkerMetrics::EventType> start_worker_first_purpose_;
+
   base::WeakPtrFactory<ServiceWorkerVersion> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerVersion);