Service Worker: Improve error messages from register().

content/browser/service_worker/service_worker_script_cache_map.h

Index: content/browser/service_worker/service_worker_script_cache_map.h
diff --git a/content/browser/service_worker/service_worker_script_cache_map.h b/content/browser/service_worker/service_worker_script_cache_map.h
index de814c210b17d6d579ecd79b4f92b04a02d363ec..7650517c7aa93e52d6358fa16cdf0790a390bda9 100644
--- a/content/browser/service_worker/service_worker_script_cache_map.h
+++ b/content/browser/service_worker/service_worker_script_cache_map.h
@@ -35,7 +35,8 @@ class CONTENT_EXPORT ServiceWorkerScriptCacheMap {
   void NotifyStartedCaching(const GURL& url, int64 resource_id);
   void NotifyFinishedCaching(const GURL& url,
                              int64 size_bytes,
-                             const net::URLRequestStatus& status);
+                             const net::URLRequestStatus& status,
+                             const std::string& status_message);
 
   // Used to retrieve the results of the initial run of a new version.
   void GetResources(
@@ -51,6 +52,10 @@ class CONTENT_EXPORT ServiceWorkerScriptCacheMap {
     return main_script_status_;
   }
 
+  const std::string& main_script_status_message() const {
+    return main_script_status_message_;
+  }
+
  private:
   typedef std::map<GURL, ServiceWorkerDatabase::ResourceRecord> ResourceMap;
 
@@ -65,6 +70,7 @@ class CONTENT_EXPORT ServiceWorkerScriptCacheMap {
   base::WeakPtr<ServiceWorkerContextCore> context_;
   ResourceMap resource_map_;
   net::URLRequestStatus main_script_status_;
+  std::string main_script_status_message_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerScriptCacheMap);
 };