Add tests for resolveRelativeUri() and a workaround.

pkg/analyzer/test/generated/utilities_dart_test.dart

Index: pkg/analyzer/test/generated/utilities_dart_test.dart
diff --git a/pkg/analyzer/test/generated/utilities_dart_test.dart b/pkg/analyzer/test/generated/utilities_dart_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c300c21d6f7bf99c134bc3153dbc665f089aa0e4
--- /dev/null
+++ b/pkg/analyzer/test/generated/utilities_dart_test.dart
@@ -0,0 +1,51 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library analyzer.test.generated.utilities_dart_test;
+
+import 'package:analyzer/src/generated/utilities_dart.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+import 'package:unittest/unittest.dart';
+
+import '../utils.dart';
+
+main() {
+  initializeTestEnvironment();
+  defineReflectiveTests(ResolveRelativeUriTest);
+}
+
+@reflectiveTest
+class ResolveRelativeUriTest {
+  void test_absolute() {
+    _validate('dart:core', 'dart:async', 'dart:async');
+    _validate('package:foo/foo.dart', 'dart:async', 'dart:async');
+    _validate('package:a/a.dart', 'package:b/b.dart', 'package:b/b.dart');
+    _validate('foo.dart', 'dart:async', 'dart:async');
+  }
+
+  void test_absoluteDart_relative() {
+    _validate('dart:core', 'int.dart', 'dart:core/int.dart');
+  }
+
+  void test_absolutePackage_relative() {
+    _validate('package:a/b.dart', 'c.dart', 'package:a/c.dart');
+    _validate('package:a/b/c.dart', 'd.dart', 'package:a/b/d.dart');
+    _validate('package:a/b/c.dart', '../d.dart', 'package:a/d.dart');
+  }
+
+  void test_relative_relative() {
+    _validate('a/b.dart', 'c.dart', 'a/c.dart');
+    _validate('a/b.dart', '../c.dart', 'c.dart');
+    _validate('a.dart', '../b.dart', '../b.dart');
+    _validate('a.dart', '../../b.dart', '../../b.dart');
+    // TODO(scheglov) After https://github.com/dart-lang/sdk/issues/27447
+    // TODO(scheglov) include also this, currently failing test.
+//    _validate('a/b.dart', '../../c.dart', '../c.dart');
+  }
+
+  void _validate(String base, String contained, String expected) {
+    Uri actual = resolveRelativeUri(Uri.parse(base), Uri.parse(contained));
+    expect(actual.toString(), expected);
+  }
+}