service worker: Propagate navigation preload flag to SWVersion.

content/browser/service_worker/service_worker_version.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_
 
 #include <stdint.h>
 
 #include <functional>
@@ skipping 152 matching lines @@
     foreign_fetch_scopes_ = scopes;
   }
 
   const std::vector<url::Origin>& foreign_fetch_origins() const {
     return foreign_fetch_origins_;
   }
   void set_foreign_fetch_origins(const std::vector<url::Origin>& origins) {
     foreign_fetch_origins_ = origins;
   }
 
+  // Only meaningful if this version is active.
   bool navigation_preload_enabled() const {
+    DCHECK(status_ == ACTIVATING || status_ == ACTIVATED) << status_;
     return navigation_preload_enabled_;
   }
+  // Only intended for use by ServiceWorkerRegistration. Generally use
+  // ServiceWorkerRegistration::EnableNavigationPreload instead of this
+  // function.
   void set_navigation_preload_enabled(bool enabled) {
     navigation_preload_enabled_ = enabled;
   }
 
   ServiceWorkerMetrics::Site site_for_uma() const { return site_for_uma_; }
 
   // This sets the new status and also run status change callbacks
   // if there're any (see RegisterStatusChangeCallback).
   void SetStatus(Status status);
 
@@ skipping 537 matching lines @@
   void CleanUpExternalRequest(const std::string& request_uuid,
                               ServiceWorkerStatusCode status);
 
   const int64_t version_id_;
   const int64_t registration_id_;
   const GURL script_url_;
   const GURL scope_;
   std::vector<GURL> foreign_fetch_scopes_;
   std::vector<url::Origin> foreign_fetch_origins_;
   FetchHandlerExistence fetch_handler_existence_;
+  // The source of truth for navigation preload state is the
+  // ServiceWorkerRegistration. |navigation_preload_enabled_| is essentially a
+  // cache for the state because it must be looked up quickly and a live
+  // registration doesn't necessarily exist whenever there is a live version.
   bool navigation_preload_enabled_ = false;
   ServiceWorkerMetrics::Site site_for_uma_;
 
   Status status_ = NEW;
   std::unique_ptr<EmbeddedWorkerInstance> embedded_worker_;
   std::vector<StatusCallback> start_callbacks_;
   std::vector<StatusCallback> stop_callbacks_;
   std::vector<base::Closure> status_change_callbacks_;
 
   // Holds in-flight requests, including requests due to outstanding push,
@@ skipping 145 matching lines @@
 
   // At this point |this| can have been deleted, so don't do anything other
   // than returning.
 
   return true;
 }
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_