Use ByteStream in downloads system to decouple source and sink.

content/browser/download/download_net_log_parameters.h

Index: content/browser/download/download_net_log_parameters.h
diff --git a/content/browser/download/download_net_log_parameters.h b/content/browser/download/download_net_log_parameters.h
index c52b87e5bfab8444d2a065d4bdfc78b7a4b64e5b..fe4bdfeede4598716a25abca8fc6286f1a70876f 100644
--- a/content/browser/download/download_net_log_parameters.h
+++ b/content/browser/download/download_net_log_parameters.h
@@ -155,6 +155,20 @@ class FileOpenedParameters : public net::NetLog::EventParameters {
   DISALLOW_COPY_AND_ASSIGN(FileOpenedParameters);
 };
 
+// NetLog parameters when a DownloadFile is opened.
+class FilePipeDrainedParameters : public net::NetLog::EventParameters {
+ public:
+  FilePipeDrainedParameters(size_t pipe_size,
+                            size_t num_buffers);
+  virtual base::Value* ToValue() const OVERRIDE;
+
+ private:
+  const size_t pipe_size_;
+  const size_t num_buffers_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePipeDrainedParameters);
+};
+
 // NetLog parameters when a DownloadFile is renamed.
 class FileRenamedParameters : public net::NetLog::EventParameters {
  public: