[Offline Pages] Turn Offliner::Cancel into an async operation to resolve conflicting assumptions

components/offline_pages/core/background/request_coordinator.h

Index: components/offline_pages/core/background/request_coordinator.h
diff --git a/components/offline_pages/core/background/request_coordinator.h b/components/offline_pages/core/background/request_coordinator.h
index 09606f2e71bf67e3e28f69c0b188179ebc571ef3..80b385ab61b58c68d671e9cc0123ebbe0b8c6ba9 100644
--- a/components/offline_pages/core/background/request_coordinator.h
+++ b/components/offline_pages/core/background/request_coordinator.h
@@ -255,6 +255,18 @@ class RequestCoordinator : public KeyedService,
   void HandleRemovedRequests(RequestNotifier::BackgroundSavePageResult status,
                              std::unique_ptr<UpdateRequestsResult> result);
 
+  void HandleCancelStopStatusCallback(

[fgorski, 2017/02/27 18:07:25]

Given Pete's concerns in the implementation, perhaps you could add some
documentation to this section, explaining how the calls are chained, which can
in turn help you naming the functions appropriately. 

[chili, 2017/02/28 00:44:14]

Done.

+      const Offliner::CancelCallback& next_callback,
+      Offliner::RequestStatus stop_status,
+      int64_t offline_id);
+  void HandleCancelRecordResultCallback(
+      const Offliner::CancelCallback& next_callback,
+      Offliner::RequestStatus stop_status,
+      int64_t offline_id);
+  void ResetActiveRequestCallback(int64_t offline_id);
+  void StartSchedulerCallback(int64_t offline_id);
+  void TryNextRequestCallback(int64_t offline_id);
+
   bool StartProcessingInternal(const ProcessingWindowState processing_state,
                                const base::Callback<void(bool)>& callback);
 
@@ -299,7 +311,8 @@ class RequestCoordinator : public KeyedService,
   void HandleWatchdogTimeout();
 
   // Cancels an in progress pre-rendering, and updates state appropriately.
-  void StopPrerendering(Offliner::RequestStatus stop_status);
+  void StopPrerendering(const Offliner::CancelCallback& callback,
+                        Offliner::RequestStatus stop_status);
 
   // Marks attempt on the request and sends it to offliner in continuation.
   void SendRequestToOffliner(const SavePageRequest& request);