Add an Error class for ServiceWorkers

public/platform/WebServiceWorkerProvider.h

Index: public/platform/WebServiceWorkerProvider.h
diff --git a/public/platform/WebServiceWorkerProvider.h b/public/platform/WebServiceWorkerProvider.h
index c7f0dc06fa7d05b8a6a356290cdc677a75f6bb78..8ee91ff3802575ddf6d5435f1d4a8fae2faf8081 100644
--- a/public/platform/WebServiceWorkerProvider.h
+++ b/public/platform/WebServiceWorkerProvider.h
@@ -38,10 +38,12 @@ namespace WebKit {
 class WebString;
 class WebURL;
 class WebServiceWorker;
+struct WebServiceWorkerError;
 
 class WebServiceWorkerProvider {
 public:
-    typedef WebCallbacks<WebServiceWorker, WebServiceWorker> WebServiceWorkerCallbacks;
+    // In callbacks, the WebServiceWorker and WebServiceWorkerError are owned by the caller and should not be freed by the implementation of this class.

[michaeln, 2013/10/16 01:19:16]

This interface is not making sense to me?

The error is a simple struct that wraps a number and a string, i get how that
works, struct goes on stack, error callback is invoked, boom done fine and good.

The worker ptr is a different matter. The class currently has no methods defined
on it, but that will change such that the class will have virtual methods
defined in the webkitapi and those methods will be overriden and implemented by
chrome... is that right? And the impl will have some state in it, at a minimum
the 'id' that idenfies the worker instance... is that right?

I don't see how chrome possibly knows when to delete it, i'm off to find other
code to see how this fits together?

+    typedef WebCallbacks<WebServiceWorker, WebServiceWorkerError> WebServiceWorkerCallbacks;
     virtual void registerServiceWorker(const WebURL& pattern, const WebURL& scriptUrl, WebServiceWorkerCallbacks*) { }
 
     virtual void unregisterServiceWorker(const WebURL& pattern, WebServiceWorkerCallbacks*) { }