Push API: define push event on Service Worker.

public/web/WebServiceWorkerContextProxy.h

Index: public/web/WebServiceWorkerContextProxy.h
diff --git a/public/web/WebServiceWorkerContextProxy.h b/public/web/WebServiceWorkerContextProxy.h
index fb3c7a8c065ed16505bfa29efab9ba96204b26d1..b689f883a9d145d1f36c523b9153b1192082abae 100644
--- a/public/web/WebServiceWorkerContextProxy.h
+++ b/public/web/WebServiceWorkerContextProxy.h
@@ -35,6 +35,7 @@
 
 namespace blink {
 
+class WebServiceWorkerPushEventCallback;
 class WebString;
 
 // A proxy interface to talk to the worker's GlobalScope implementation.
@@ -54,6 +55,10 @@ public:
     // Once the ServiceWorker has finished handling the sync event
     // didHandleSyncEvent is called on the context client.
     virtual void dispatchSyncEvent(int syncEventID) = 0;
+
+    // Once the ServiceWorker has finished handling the push event
+    // the callback is run.
+    virtual void dispatchPushEvent(int eventID, const WebString& data, const WebServiceWorkerPushEventCallback&) = 0;

[kinuko, 2014/05/22 04:33:19]

nit: this callback interface doesn't look particularly useful to me at least in
the current code, especially if it's always called at the end of
dispatchPushEvent method.  Will there be a case where we call the given callback
asyncly, with additional status info like success or failure?  (I guess the same
comment applies to SyncEvent one)

[Michael van Ouwerkerk, 2014/05/23 18:32:03]

I hoped you would know what this is for, this is the existing pattern. It seems
ServiceWorkerVersion likes to track these callbacks in the browser process.

In future, this may be relevant in context of limiting execution time. The
callback value would be different if the script is killed:
https://code.google.com/p/chromium/issues/detail?id=372436

For now, the callback is an interesting problem to be solved for modular
addition of API's that live in Service Worker.

[kinuko, 2014/05/26 04:03:00]

Two questions:

* I know this is from the existing pattern, I just wonder if we could just do
something like below in the chromium side (in service_worker_script_context.cc)
if it doesn't need to be called back asyncly:

dispatchPushEvent();
DidHandlePushEvent(request_id);

* If this follows the existing pattern should we really want to apply a callback
pattern only for this method now?  I can see some benefits for using the pattern
here (it removes some additional plumbing for calling back to chromium side),
but I also feel it'd make these interfaces a bit  inconsistent.  In other words,
say, if we want to convert all the dispatch*Event() stuff into this pattern do
we need to define new callback types for each of them?

 };
 
 } // namespace blink