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

pkg/compiler/lib/src/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
 import '../common/resolution.dart' show Resolution, ParsingContext;
 import '../compiler.dart' show Compiler;
@@ skipping 749 matching lines @@
     if (!localMembers.isEmpty) {
       reporter.reportErrorMessage(tag, MessageKind.BEFORE_TOP_LEVEL);
       return;
     }
     if (partTag != null) {
       reporter.reportWarningMessage(tag, MessageKind.DUPLICATED_PART_OF);
       return;
     }
     partTag = tag;
     LibraryName libraryTag = library.libraryTag;
+
+    Expression libraryReference = tag.name;
+    if (libraryReference is LiteralString) {
+      // Name is a URI. Resolve and compare to library's URI.
+      String content = libraryReference.dartString.slowToString();
+      Uri uri = this.script.readableUri.resolve(content);
+      Uri expectedUri = library.canonicalUri;
+      if (uri != expectedUri) {
+        // Consider finding a relative URI reference for the error message.
+        reporter.reportWarningMessage(tag.name,
+            MessageKind.LIBRARY_URI_MISMATCH, {'libraryUri': expectedUri});
+      }
+      return;
+    }
     String actualName = tag.name.toString();
     if (libraryTag != null) {
       String expectedName = libraryTag.name.toString();
       if (expectedName != actualName) {
         reporter.reportWarningMessage(tag.name,
             MessageKind.LIBRARY_NAME_MISMATCH, {'libraryName': expectedName});
       }
     } else {
       reporter.reportWarning(
           reporter.createMessage(library, MessageKind.MISSING_LIBRARY_NAME,
@@ skipping 2687 matching lines @@
       body = node.asFunctionExpression().body;
     }
     return new ParsedResolvedAst(
         declaration,
         node,
         body,
         definingElement.treeElements,
         definingElement.compilationUnit.script.resourceUri);
   }
 }