[Background Fetch] Cleanup/fix thread safety

content/browser/background_fetch/background_fetch_context.h

 // Copyright 2017 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_BACKGROUND_FETCH_BACKGROUND_FETCH_CONTEXT_H_
 #define CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_CONTEXT_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 21 matching lines @@
 class BackgroundFetchRegistrationId;
 class BackgroundFetchRequestInfo;
 class BlobHandle;
 class BrowserContext;
 class ServiceWorkerContextWrapper;
 struct ServiceWorkerFetchRequest;
 class StoragePartitionImpl;
 
 // The BackgroundFetchContext is the central moderator of ongoing background
 // fetch requests from the Mojo service and from other callers.
-// Background Fetch requests function similar to normal fetches except that
+// Background Fetch requests function similarly to normal fetches except that
 // they are persistent across Chromium or service worker shutdown.
 class CONTENT_EXPORT BackgroundFetchContext
     : public base::RefCountedThreadSafe<BackgroundFetchContext,
-                                        BrowserThread::DeleteOnUIThread> {
+                                        BrowserThread::DeleteOnIOThread> {
  public:
   // The BackgroundFetchContext will watch the ServiceWorkerContextWrapper so
   // that it can respond to service worker events such as unregister.
   BackgroundFetchContext(BrowserContext* browser_context,
                          StoragePartitionImpl* storage_partition,
                          scoped_refptr<ServiceWorkerContextWrapper> context);
 
   // Finishes initializing the Background Fetch context on the IO thread by
   // setting the |request_context_getter|.
   void InitializeOnIOThread(
       scoped_refptr<net::URLRequestContextGetter> request_context_getter);
 
-  // Shutdown must be called before deleting this. Call on the UI thread.
-  void Shutdown();
-
   // Starts a Background Fetch for the |registration_id|. The |requests| will be
   // asynchronously fetched. The |callback| will be invoked when the fetch has
   // been registered, or an error occurred that avoids it from doing so.
   void StartFetch(const BackgroundFetchRegistrationId& registration_id,
                   const std::vector<ServiceWorkerFetchRequest>& requests,
                   const BackgroundFetchOptions& options,
                   blink::mojom::BackgroundFetchService::FetchCallback callback);
 
   // Returns a vector with the tags of the active fetches for the given |origin|
   // and |service_worker_registration_id|.
   std::vector<std::string> GetActiveTagsForServiceWorkerRegistration(
       int64_t service_worker_registration_id,
       const url::Origin& origin) const;
 
   // Returns the JobController that is handling the |registration_id|, or a
   // nullptr if it does not exist. Must be immediately used by the caller.
   BackgroundFetchJobController* GetActiveFetch(
       const BackgroundFetchRegistrationId& registration_id) const;
 
  private:
   friend class base::DeleteHelper<BackgroundFetchContext>;
-  friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
+  friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>;
   friend class base::RefCountedThreadSafe<BackgroundFetchContext,
-                                          BrowserThread::DeleteOnUIThread>;
+                                          BrowserThread::DeleteOnIOThread>;
 
   ~BackgroundFetchContext();
 
-  // Shuts down the active Job Controllers on the IO thread.
-  void ShutdownOnIO();
-
   // Creates a new Job Controller for the given |registration_id| and |options|,
   // which will start fetching the files that are part of the registration.
   void CreateController(
       const BackgroundFetchRegistrationId& registration_id,
       const BackgroundFetchOptions& options,
       std::vector<scoped_refptr<BackgroundFetchRequestInfo>> initial_requests);
 
   // Called when a new registration has been created by the data manager.
   void DidCreateRegistration(
       const BackgroundFetchRegistrationId& registration_id,
@@ skipping 32 matching lines @@
   std::map<BackgroundFetchRegistrationId,
            std::unique_ptr<BackgroundFetchJobController>>
       active_fetches_;
 
   DISALLOW_COPY_AND_ASSIGN(BackgroundFetchContext);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BACKGROUND_FETCH_BACKGROUND_FETCH_CONTEXT_H_