Implement Drain() on HttpPipelinedStream.

net/http/http_pipelined_connection_impl.h

Index: net/http/http_pipelined_connection_impl.h
diff --git a/net/http/http_pipelined_connection_impl.h b/net/http/http_pipelined_connection_impl.h
index 6a7f3859f8102f809edbe52a7de4ba6c1c2ad225..a63aabd0d430167e2d5e652f65e82acdbe55d28f 100644
--- a/net/http/http_pipelined_connection_impl.h
+++ b/net/http/http_pipelined_connection_impl.h
@@ -28,6 +28,7 @@ namespace net {
 
 class ClientSocketHandle;
 class GrowableIOBuffer;
+class HttpNetworkSession;
 class HttpRequestHeaders;
 class HttpResponseInfo;
 class IOBuffer;
@@ -117,6 +118,10 @@ class NET_EXPORT_PRIVATE HttpPipelinedConnectionImpl
   void GetSSLCertRequestInfo(int pipeline_id,
                              SSLCertRequestInfo* cert_request_info);
 
+  // Attempts to drain the response body for |stream| so that the pipeline may
+  // be reused.
+  void Drain(HttpPipelinedStream* stream, HttpNetworkSession* session);
+
  private:
   enum StreamState {
     STREAM_CREATED,