[extension SW] Support lazy events from extension service workers.

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 9a9aa0a823a13218c9f0e3a37a533eaf6ea702f8..0cfa362c02bf3778c5548d5d2fc90bd5c3682d69 100644
--- a/content/public/browser/service_worker_context.h
+++ b/content/public/browser/service_worker_context.h
@@ -58,6 +58,9 @@ class ServiceWorkerContext {
   using StartServiceWorkerForNavigationHintCallback =
       base::Callback<void(StartServiceWorkerForNavigationHintResult result)>;
 
+  using GetWorkerInfoCallback =
+      base::OnceCallback<void(int process_id, int thread_id)>;
+
   // Registers the header name which should not be passed to the ServiceWorker.
   // Must be called from the IO thread.
   CONTENT_EXPORT static void AddExcludedHeadersForFetchEvent(
@@ -107,6 +110,16 @@ class ServiceWorkerContext {
   virtual bool FinishedExternalRequest(int64_t service_worker_version_id,
                                        const std::string& request_uuid) = 0;
 
+  // Starts a previously registered worker at |origin| and returns running

[falken, 2017/06/22 03:35:57]

Starts the active worker of the registration whose scope is |pattern| and...

[lazyboy, 2017/06/23 02:18:30]

Done.

+  // worker info via |info_callback|.
+  // |info_callback| contains worker render process id and worker thread id.

[falken, 2017/06/22 03:35:57]

Is "contains" the conventional wording for a callback? I would have said
"|info_callback| is passed the worker's render process..."

[lazyboy, 2017/06/23 02:18:30]

That's better, thanks.
Done.

+  //
+  // Must be called on IO thread.
+  virtual void GetWorkerInfoAfterStartWorker(
+      const GURL& origin,

[falken, 2017/06/22 03:35:57]

|origin| looks weird to me because an origin can have multiple registrations,
and a registration has multiple workers.

What is being passed here? Since function uses FindReadyRegistrationForPattern
you must pass in a pattern here that is identical to the registration's pattern
(i.e., it doesn't do a prefix match like FindReadyRegistrationForDocument uses).

So I think this should be called
GetWorkerInfoAfterStartActiveWorkerForPattern(const GURL& pattern, ...)

or maybe just StartActiveWorkerForPattern.

[lazyboy, 2017/06/23 02:18:30]

It is origin + scope,
For example,
chrome-extension://pdbihmnjpcgicblhmommoeoegalabckg/
where the extension pdbihmnjpcgicblhmommoeoegalabckg registered a service worker
on the scope '/'.

I've changed the references to origin in the CL to pattern.

 Since function uses FindReadyRegistrationForPattern
Changed to StartActiveWorkerForPattern

+      GetWorkerInfoCallback info_callback,
+      base::OnceClosure failure_callback) = 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