Add a general purpose facility for letting background tasks wait until

components/offline_pages/background/request_coordinator.h

 // Copyright 2016 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 COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_COORDINATOR_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_COORDINATOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 29 matching lines @@
 
   ~RequestCoordinator() override;
 
   // Queues |request| to later load and save when system conditions allow.
   // Returns true if the page could be queued successfully.
   bool SavePageLater(const GURL& url, const ClientId& client_id);
 
   // Starts processing of one or more queued save page later requests.
   // Returns whether processing was started and that caller should expect
   // a callback. If processing was already active, returns false.
-  bool StartProcessing(const base::Callback<void(bool)>& callback);
+  bool StartProcessing(const base::Callback<void(bool)> callback);
 
   // Stops the current request processing if active. This is a way for
   // caller to abort processing; otherwise, processing will complete on
   // its own. In either case, the callback will be called when processing
   // is stopped or complete.
   void StopProcessing();
 
   // Returns the request queue used for requests.  Coordinator keeps ownership.
   RequestQueue* queue() { return queue_.get(); }
 
@@ skipping 25 matching lines @@
   // OfflinerFactory.  Used to create offline pages. Owned.
   std::unique_ptr<OfflinerFactory> factory_;
   // RequestQueue.  Used to store incoming requests. Owned.
   std::unique_ptr<RequestQueue> queue_;
   // Scheduler. Used to request a callback when network is available.  Owned.
   std::unique_ptr<Scheduler> scheduler_;
   // Status of the most recent offlining.
   Offliner::RequestStatus last_offlining_status_;
   // Class to choose which request to schedule next
   std::unique_ptr<RequestPicker> picker_;
+  // Calling this returns to the scheduler across the JNI bridge.
+  base::Callback<void(bool)> scheduler_callback_;
   // Allows us to pass a weak pointer to callbacks.
   base::WeakPtrFactory<RequestCoordinator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RequestCoordinator);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_COORDINATOR_H_