[Offline Prefetch] Backoff support for PrefetchBackgroundTask

components/offline_pages/core/prefetch/prefetch_dispatcher.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 COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_DISPATCHER_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_DISPATCHER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 21 matching lines @@
   };
 
   // A |ScopedBackgroundTask| is created when we are running in a background
   // task.  Destroying this object should notify the system that we are done
   // processing the background task.
   class ScopedBackgroundTask {
    public:
     ScopedBackgroundTask() = default;
     virtual ~ScopedBackgroundTask() = default;
 
-    // Used on destruction to inform the system about whether rescheduling is
-    // required.
-    virtual void SetNeedsReschedule(bool reschedule) = 0;
+    // Used on destruction to inform the system about whether rescheduling with
+    // or without backoff is required.
+    virtual void SetNeedsReschedule(bool reschedule, bool backoff) = 0;
   };
 
   virtual ~PrefetchDispatcher() = default;
 
   // Called when a consumer has candidate URLs for the system to prefetch.
   // Duplicates are accepted by the PrefetchDispatcher but ignored.
   virtual void AddCandidatePrefetchURLs(
       const std::vector<PrefetchURL>& prefetch_urls) = 0;
 
   // Called when all existing suggestions are no longer considered valid for a
   // given namespace.  The prefetch system should remove any URLs that
   // have not yet started downloading within that namespace.
   virtual void RemoveAllUnprocessedPrefetchURLs(
       const std::string& name_space) = 0;
 
   // Called to invalidate a single PrefetchURL entry identified by |client_id|.
   // If multiple have the same |client_id|, they will all be removed.
   virtual void RemovePrefetchURLsByClientId(const ClientId& client_id) = 0;
 
   // Called when Android OS has scheduled us for background work.  When
   // destroyed, |task| will call back and inform the OS that we are done work
   // (if required).  |task| also manages rescheduling behavior.
   virtual void BeginBackgroundTask(
       std::unique_ptr<ScopedBackgroundTask> task) = 0;
 
   // Called when a task must stop immediately due to system constraints. After
   // this call completes, the system will reschedule the task based on whether
   // SetNeedsReschedule has been called.
-  virtual void StopBackgroundTask(ScopedBackgroundTask* task) = 0;
+  virtual void StopBackgroundTask(bool signaled_by_system) = 0;

[dewittj, 2017/05/31 21:33:33]

Instead of signaled_by_system, can you please have a
RequestFinishBackgroundTaskForTest() that can be used in testing? Otherwise the
parameter implies functionality that just doesn't exist in the production
system.

[jianli, 2017/06/01 00:09:59]

Done.

 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_DISPATCHER_H_