Support auto-drain of HttpRequest data.

sdk/lib/io/http.dart

Index: sdk/lib/io/http.dart
diff --git a/sdk/lib/io/http.dart b/sdk/lib/io/http.dart
index 5dc573871c73983f8114d33e299f6de4667d2169..913ab8f84845f7fbb05bbb5a615b5cf9d5ba6e2e 100644
--- a/sdk/lib/io/http.dart
+++ b/sdk/lib/io/http.dart
@@ -721,6 +721,10 @@ abstract class HttpRequest implements Stream<List<int>> {
   /**
    * Gets the [HttpResponse] object, used for sending back the response to the
    * client.
+   *
+   * If the [contentLength] of the body isn't 0, and the body isn't being read,
+   * any write calls on the [HttpResponse] will automatically drain the request
+   * body.
    */
   HttpResponse get response;
 }