Switch pkg packages, pub, and dartdoc to use package: imports.

pkg/oauth2/lib/src/authorization_code_grant.dart

Index: pkg/oauth2/lib/src/authorization_code_grant.dart
diff --git a/pkg/oauth2/lib/src/authorization_code_grant.dart b/pkg/oauth2/lib/src/authorization_code_grant.dart
index 342c726bbad66cd7d9e1ab60eefd76d0eff41ff8..900dfc536f6986312c4e5f5a16e28976583bb95a 100644
--- a/pkg/oauth2/lib/src/authorization_code_grant.dart
+++ b/pkg/oauth2/lib/src/authorization_code_grant.dart
@@ -7,8 +7,7 @@ library authorization_code_grant;
 import 'dart:async';
 import 'dart:uri';
 
-// TODO(nweiz): This should be a "package:" import. See issue 6745.
-import '../../../../pkg/http/lib/http.dart' as http;
+import 'package:http/http.dart' as http;
 
 import 'client.dart';
 import 'authorization_exception.dart';