Fix for resolveRelativeUri() when the containedUri is absolute.

pkg/analyzer/test/generated/all_the_rest_test.dart

 // Copyright (c) 2014, 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.all_the_rest_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 4146 matching lines @@
     expect(relative.toString(), "dart:test/lib.dart");
   }
 
   void test_resolveRelative_dart_filePath() {
     Uri uri = parseUriWithException("dart:test");
     Uri relative = resolveRelativeUri(uri, parseUriWithException("c/lib.dart"));
     expect(relative, isNotNull);
     expect(relative.toString(), "dart:test/c/lib.dart");
   }
 
+  void test_resolveRelative_dart_dartUri() {
+    Uri uri = parseUriWithException('dart:foo');
+    Uri relative = resolveRelativeUri(uri, parseUriWithException('dart:bar'));
+    expect(relative, isNotNull);
+    expect(relative.toString(), 'dart:bar');
+  }
+
   void test_resolveRelative_dart_filePathWithParent() {
     Uri uri = parseUriWithException("dart:test/b/test.dart");
     Uri relative =
         resolveRelativeUri(uri, parseUriWithException("../c/lib.dart"));
     expect(relative, isNotNull);
     expect(relative.toString(), "dart:test/c/lib.dart");
   }
 
   void test_resolveRelative_package_fileName() {
     Uri uri = parseUriWithException("package:b/test.dart");
     Uri relative = resolveRelativeUri(uri, parseUriWithException("lib.dart"));
     expect(relative, isNotNull);
     expect(relative.toString(), "package:b/lib.dart");
   }
 
   void test_resolveRelative_package_fileNameWithoutPackageName() {
     Uri uri = parseUriWithException("package:test.dart");
     Uri relative = resolveRelativeUri(uri, parseUriWithException("lib.dart"));
     expect(relative, isNotNull);
     expect(relative.toString(), "package:lib.dart");
   }
 
+  void test_resolveRelative_package_dartUri() {
+    Uri uri = parseUriWithException('package:foo/bar.dart');
+    Uri relative = resolveRelativeUri(uri, parseUriWithException('dart:test'));
+    expect(relative, isNotNull);
+    expect(relative.toString(), 'dart:test');
+  }
+
   void test_resolveRelative_package_filePath() {
     Uri uri = parseUriWithException("package:b/test.dart");
     Uri relative = resolveRelativeUri(uri, parseUriWithException("c/lib.dart"));
     expect(relative, isNotNull);
     expect(relative.toString(), "package:b/c/lib.dart");
   }
 
   void test_resolveRelative_package_filePathWithParent() {
     Uri uri = parseUriWithException("package:a/b/test.dart");
     Uri relative =
@@ skipping 86 matching lines @@
     expect(UriKind.fromEncoding(0x70), same(UriKind.PACKAGE_URI));
     expect(UriKind.fromEncoding(0x58), same(null));
   }
 
   void test_getEncoding() {
     expect(UriKind.DART_URI.encoding, 0x64);
     expect(UriKind.FILE_URI.encoding, 0x66);
     expect(UriKind.PACKAGE_URI.encoding, 0x70);
   }
 }