Handle early pause, cancel for parallel requests.

content/browser/download/parallel_download_job.h

Index: content/browser/download/parallel_download_job.h
diff --git a/content/browser/download/parallel_download_job.h b/content/browser/download/parallel_download_job.h
index 3beafc979b735250dae963ae2e8680637a15aa65..6f5a7bd98a3b58dad5865330897c430061749115 100644
--- a/content/browser/download/parallel_download_job.h
+++ b/content/browser/download/parallel_download_job.h
@@ -39,18 +39,24 @@ class CONTENT_EXPORT ParallelDownloadJob : public DownloadJobImpl,
   // Virtual for testing.
   virtual int GetParallelRequestCount() const;
 
- private:
-  friend class ParallelDownloadJobTest;
-
   using WorkerMap =
       std::unordered_map<int64_t, std::unique_ptr<DownloadWorker>>;
 
+  // Map from the offset position of the slice to the worker that downloads the
+  // slice.
+  WorkerMap workers_;
+
+ private:
+  friend class ParallelDownloadJobTest;
+
   // DownloadWorker::Delegate implementation.
   void OnByteStreamReady(
       DownloadWorker* worker,
       std::unique_ptr<ByteStreamReader> stream_reader) override;
   void OnServerResponseError(DownloadWorker* worker,
                              DownloadInterruptReason reason) override;
+  bool IsPaused() const override;

[qinmin, 2017/03/22 05:50:29]

nit: worker can remember whether pause() is called or not, no need to ask the
delegate

[xingliu, 2017/03/22 23:54:06]

We may pause/cancel before the worker is constructed.

Alternatively we need to pass the current state to worker's constructor, which
looks more weird. I think duplicate states can easily introduce bugs.

This is caught in the unit test, when I move the is_pause into the worker.

[qinmin, 2017/03/24 19:52:58]

wait, if we pause/cancel before worker is constructed, why do we create the
workers.

+  bool IsCanceled() const override;
 
   // Build parallel requests after a delay, to effectively measure the single
   // stream bandwidth.
@@ -74,10 +80,6 @@ class CONTENT_EXPORT ParallelDownloadJob : public DownloadJobImpl,
   // the size of the target file if the request starts from non-zero offset.
   int64_t content_length_;
 
-  // Map from the offset position of the slice to the worker that downloads the
-  // slice.
-  WorkerMap workers_;
-
   // Used to send parallel requests after a delay based on Finch config.
   base::OneShotTimer timer_;