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

pkg/analyzer/test/src/context/context_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.src.context.context_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 748 matching lines @@
     List<AnalysisError> errors = context.computeErrors(source);
     expect(errors, hasLength(0));
   }
 
   void test_computeErrors_dart_part() {
     Source librarySource =
         addSource("/lib.dart", "library lib; part 'part.dart';");
     Source partSource = addSource("/part.dart", "part of 'lib';");
     context.parseCompilationUnit(librarySource);
     List<AnalysisError> errors = context.computeErrors(partSource);
-    expect(errors, isNotNull);
-    expect(errors.length > 0, isTrue);
+    if (context.analysisOptions.enableUriInPartOf) {
+      // TODO(28522)
+      // Should report that 'lib' isn't the correct URI.
+    } else {
+      expect(errors, isNotNull);
+      expect(errors.length > 0, isTrue);
+    }
   }
 
   void test_computeErrors_dart_some() {
     Source source = addSource("/lib.dart", "library 'lib';");
     List<AnalysisError> errors = context.computeErrors(source);
     expect(errors, isNotNull);
     expect(errors.length > 0, isTrue);
   }
 
   void test_computeErrors_html_none() {
@@ skipping 4659 matching lines @@
    * Initialize the visitor.
    */
   _ElementGatherer();
 
   @override
   void visitElement(Element element) {
     elements[element] = element;
     super.visitElement(element);
   }
 }