Make Analyzer, VM and dart2js accept URI strings as part-of library identifier.

pkg/analyzer/test/src/dart/analysis/driver_test.dart

 // 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.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 396 matching lines @@
     provider.newFile(
         part,
         '''
 part of lib;
 ''');
 
     driver.addFile(lib);
 
     AnalysisResult libResult = await driver.getResult(lib);
     List<AnalysisError> errors = libResult.errors;
-    expect(errors, hasLength(1));
-    expect(errors[0].errorCode,
-        ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART);
+    if (libResult.unit.element.context.analysisOptions.enableUriInPartOf) {
+      // TODO(28522): Should cause an error for wrong library name.
+      expect(errors, hasLength(0));
+    } else {
+        expect(errors, hasLength(1));
+        expect(errors[0].errorCode,
+            ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART);
+    }
   }
 
   test_analyze_resolveDirectives_error_partOfDifferentLibrary_byName() async {
     var lib = _p('/test/lib.dart');
     var part = _p('/test/part.dart');
     provider.newFile(
         lib,
         '''
 library lib;
 part 'part.dart';
@@ skipping 1940 matching lines @@
    * Return the [provider] specific path for the given Posix [path].
    */
   String _p(String path) => provider.convertPath(path);
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }
 
 class _SourceMock extends TypedMock implements Source {}