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 3a9a5c77e363e772d0d63bd6dac3684e30f80064..12758db1dc7ed782385e0e8d88b71a5973ce4e5e 100644
--- a/content/browser/download/download_resource_handler.h
+++ b/content/browser/download/download_resource_handler.h
@@ -23,7 +23,8 @@ class DownloadRequestHandle;
 struct DownloadCreateInfo;
 
 namespace content {
-class DownloadBuffer;
+class ByteStreamInput;
+class ByteStreamOutput;
 }
 
 namespace net {
@@ -35,8 +36,6 @@ class DownloadResourceHandler : public ResourceHandler {
  public:
   typedef content::DownloadManager::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,
@@ -87,8 +86,6 @@ class DownloadResourceHandler : public ResourceHandler {
 
   void set_content_disposition(const std::string& content_disposition);
 
-  void CheckWriteProgress();
-
   std::string DebugString() const;
 
  private:
@@ -99,18 +96,20 @@ class DownloadResourceHandler : public ResourceHandler {
                                    const std::string& security_info,
                                    int response_code);
 
-  void StartPauseTimer();
   void CallStartedCB(content::DownloadId id, net::Error error);
 
   // Generates a DownloadId and calls DownloadFileManager.
   void StartOnUIThread(scoped_ptr<DownloadCreateInfo> info,
+                       scoped_ptr<content::ByteStreamOutput> pipe,
                        const DownloadRequestHandle& handle);
   void set_download_id(content::DownloadId id);
 
+  // Resume requests paused in OnReadCompleted()
+  void ResumeRequest();
+
   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_;
@@ -118,13 +117,16 @@ class DownloadResourceHandler : public ResourceHandler {
   // This is used only on the UI thread.
   OnStartedCallback started_cb_;
   content::DownloadSaveInfo save_info_;
-  scoped_refptr<content::DownloadBuffer> buffer_;
-  bool is_paused_;
-  base::OneShotTimer<DownloadResourceHandler> pause_timer_;
+
+  // Data flow
+  scoped_refptr<net::IOBuffer> read_buffer_;       // From URLRequest.
+  scoped_ptr<content::ByteStreamInput> pipe_input_; // To rest of system.
 
   // The following are used to collect stats.
   base::TimeTicks download_start_time_;
   base::TimeTicks last_read_time_;
+  base::TimeTicks last_pause_time_;
+  base::TimeDelta total_pause_time_;
   size_t last_buffer_size_;
   int64 bytes_read_;
   std::string accept_ranges_;