Use ByteStream in downloads system to decouple source and sink.

content/browser/download/download_resource_handler.h

Index: content/browser/download/download_resource_handler.h
diff --git a/content/browser/download/download_resource_handler.h b/content/browser/download/download_resource_handler.h
index 6cb273c52a97925e76020f6472cf9eb61b2e2e12..5ad89e096550c96d8180a8ee25afb20f5088a6c4 100644
--- a/content/browser/download/download_resource_handler.h
+++ b/content/browser/download/download_resource_handler.h
@@ -24,7 +24,8 @@ class DownloadRequestHandle;
 struct DownloadCreateInfo;
 
 namespace content {
-class DownloadBuffer;
+class ByteStreamInput;
+class ByteStreamOutput;
 }
 
 namespace net {
@@ -36,8 +37,6 @@ class DownloadResourceHandler : public ResourceHandler {
  public:
   typedef content::DownloadUrlParameters::OnStartedCallback OnStartedCallback;
 
-  static const size_t kLoadsToWrite = 100;  // number of data buffers queued
-
   // started_cb will be called exactly once on the UI thread.
   DownloadResourceHandler(int render_process_host_id,
                           int render_view_id,
@@ -92,21 +91,11 @@ class DownloadResourceHandler : public ResourceHandler {
  private:
   virtual ~DownloadResourceHandler();
 
-  void OnResponseCompletedInternal(int request_id,
-                                   const net::URLRequestStatus& status,
-                                   const std::string& security_info,
-                                   int response_code);
-
-  void CheckWriteProgressLater();
-  void CheckWriteProgress();
-  void MaybeResumeRequest();
+  // Arrange for started_cb_ to be called on the UI thread with the
+  // below values, nulling out started_cb_.  Should only be called
+  // on the IO thread.
   void CallStartedCB(content::DownloadId id, net::Error error);
 
-  // Generates a DownloadId and calls DownloadFileManager.
-  void StartOnUIThread(scoped_ptr<DownloadCreateInfo> info,
-                       const DownloadRequestHandle& handle);
-  void SetDownloadID(content::DownloadId id);
-
   // If the content-length header is not present (or contains something other
   // than numbers), the incoming content_length is -1 (unknown size).
   // Set the content length to 0 to indicate unknown size to DownloadManager.
@@ -114,23 +103,26 @@ class DownloadResourceHandler : public ResourceHandler {
 
   void SetContentDisposition(const std::string& content_disposition);
 
-  content::DownloadId download_id_;
   content::GlobalRequestID global_id_;
   int render_view_id_;
-  scoped_refptr<net::IOBuffer> read_buffer_;
   std::string content_disposition_;
   int64 content_length_;
   DownloadFileManager* download_file_manager_;
   net::URLRequest* request_;
-  // This is used only on the UI thread.
+  // This is read only on the IO thread, but may only
+  // be called on the UI thread.
   OnStartedCallback started_cb_;
   content::DownloadSaveInfo save_info_;
-  scoped_refptr<content::DownloadBuffer> buffer_;
-  base::OneShotTimer<DownloadResourceHandler> check_write_progress_timer_;
+
+  // Data flow
+  scoped_refptr<net::IOBuffer> read_buffer_;       // From URLRequest.
+  scoped_ptr<content::ByteStreamInput> stream_writer_; // To rest of system.
 
   // The following are used to collect stats.
   base::TimeTicks download_start_time_;
   base::TimeTicks last_read_time_;
+  base::TimeTicks last_pipe_pause_time_;
+  base::TimeDelta total_pause_time_;
   size_t last_buffer_size_;
   int64 bytes_read_;
   std::string accept_ranges_;
@@ -138,6 +130,9 @@ class DownloadResourceHandler : public ResourceHandler {
   int pause_count_;
   bool was_deferred_;
 
+  // For DCHECKing
+  bool on_response_started_called_;
+
   static const int kReadBufSize = 32768;  // bytes
   static const int kThrottleTimeMs = 200;  // milliseconds