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

pkg/oauth2/test/client_test.dart

Index: pkg/oauth2/test/client_test.dart
diff --git a/pkg/oauth2/test/client_test.dart b/pkg/oauth2/test/client_test.dart
index a815a22e5605ee1878cad30f4592d11d7d2f6ea0..7049122ba0db134098cb923fc5fc878f73c5ce85 100644
--- a/pkg/oauth2/test/client_test.dart
+++ b/pkg/oauth2/test/client_test.dart
@@ -9,9 +9,10 @@ import 'dart:io';
 import 'dart:json' as JSON;
 import 'dart:uri';
 
-import '../../../pkg/unittest/lib/unittest.dart';
-import '../../../pkg/http/lib/http.dart' as http;
-import '../lib/oauth2.dart' as oauth2;
+import 'package:http/http.dart' as http;
+import 'package:oauth2/oauth2.dart' as oauth2;
+import 'package:unittest/unittest.dart';
+
 import 'utils.dart';
 
 final Uri requestUri = Uri.parse("http://example.com/resource");