Fix some warnings in pub and pkg packages.

utils/pub/safe_http_server.dart

Index: utils/pub/safe_http_server.dart
diff --git a/utils/pub/safe_http_server.dart b/utils/pub/safe_http_server.dart
index 8843e488c1e3b2909effd630ba1cad0cb72be36c..37b16c83391044bfaba64a6d02162de4f66d994b 100644
--- a/utils/pub/safe_http_server.dart
+++ b/utils/pub/safe_http_server.dart
@@ -140,7 +140,9 @@ class _HttpResponseWrapper implements HttpResponse {
     _inner.writeStream(stream);
   Future close() => _inner.close();
   void write(Object obj) => _inner.write(obj);
-  void writeAll(Iterable objects) => _inner.writeAll(objects);
+  void writeAll(Iterable objects, [String separator = ""]) =>
+    _inner.writeAll(objects, separator);
   void writeCharCode(int charCode) => _inner.writeCharCode(charCode);
   void writeln([Object obj = ""]) => _inner.writeln(obj);
+  void addError(AsyncError error) => _inner.addError(error);
 }