Lazy creating of background pages --enable-lazy-background-pages)

chrome/browser/extensions/extension_event_router.h

Index: chrome/browser/extensions/extension_event_router.h
diff --git a/chrome/browser/extensions/extension_event_router.h b/chrome/browser/extensions/extension_event_router.h
index d46e05f867ec08594d42aa179dc5f9ca832f2f23..5307e601da8f0d4caba70675c0ca5a705a02179c 100644
--- a/chrome/browser/extensions/extension_event_router.h
+++ b/chrome/browser/extensions/extension_event_router.h
@@ -89,6 +89,15 @@ class ExtensionEventRouter : public NotificationObserver {
  protected:
   // Shared by DispatchEvent*. If |extension_id| is empty, the event is
   // broadcast.
+  // Eventually DispatchEventImpl will be called, but it may be delayed
+  // sif the extension has a lazy background page.
+  void MaybeDispatchEventImpl(
+      const std::string& extension_id,
+      const std::string& event_name,
+      const std::string& event_args,
+      Profile* restrict_to_profile,
+      const std::string& cross_incognito_args,
+      const GURL& event_url);
   virtual void DispatchEventImpl(
       const std::string& extension_id,
       const std::string& event_name,
@@ -97,10 +106,23 @@ class ExtensionEventRouter : public NotificationObserver {
       const std::string& cross_incognito_args,
       const GURL& event_url);
 
+  // Store the event and dispatch it when the background page is done loading.
+  void EnqueueEvent(const std::string& extension_id,
+                    const std::string& event_name,
+                    const std::string& event_args,
+                    Profile* restrict_to_profile,
+                    const std::string& cross_incognito_args,
+                    const GURL& event_url);
+  void DispatchPendingEvents(const std::string& extension_id);
+  void ClearPendingEvents(const std::string& extension_id);
+
  private:
   // An extension listening to an event.
   struct EventListener;
 
+  // An event that is waiting to be dispatched.
+  struct PendingEvent;
+
   virtual void Observe(int type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
@@ -116,6 +138,11 @@ class ExtensionEventRouter : public NotificationObserver {
   typedef std::map<std::string, std::set<EventListener> > ListenerMap;
   ListenerMap listeners_;
 
+  // A map between an extension id and the queue of events pending
+  // the load of it's background page.
+  typedef std::vector<PendingEvent> PendingEventsQueue;

[Aaron Boodman, 2011/08/18 19:25:55]

You can use std::queue.

[Tessa MacDuff, 2011/08/18 20:49:39]

Yeah, I just thought it was overkill since I never actually pop things off the
queue (I just iterate through it all at once and then delete the whole thing). 
I'm happy to update the rest of the code so that I don't act like it's a queue
(i.e. AppendEvent() instead of EnqueueEvent()).

[Aaron Boodman, 2011/08/18 21:19:23]

ok.

[Tessa MacDuff, 2011/08/23 18:18:42]

Done.

+  std::map<std::string, PendingEventsQueue> pending_events_;

[Aaron Boodman, 2011/08/18 19:25:55]

Nit: this is a bit inefficient because as these maps and vectors resize there
will be a lot of copying.

You can use base/linked_ptr.h, and make it like:

std::vector<linked_ptr<PendingEvent> >
std::map<std::string, linked_ptr<PendingEventsQueue> >

The linked_ptr will manage the lifetime automatically. There's other examples in
Chrome of this usage you can look for examples.

[Tessa MacDuff, 2011/08/23 18:18:42]

Done.

+
   DISALLOW_COPY_AND_ASSIGN(ExtensionEventRouter);
 };