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

pkg/compiler/lib/src/parser/parser.dart

 // Copyright (c) 2012, 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 dart2js.parser;
 
 import '../common.dart';
 import '../tokens/keyword.dart' show Keyword;
 import '../tokens/precedence.dart' show PrecedenceInfo;
 import '../tokens/precedence_constants.dart'
@@ skipping 303 matching lines @@
     token = expect(';', token);
     listener.endPart(partKeyword, semicolon);
     return token;
   }
 
   Token parsePartOf(Token token) {
     listener.beginPartOf(token);
     assert(optional('part', token));
     assert(optional('of', token.next));
     Token partKeyword = token;
-    token = parseQualified(token.next.next);
+    token = token.next.next;
+    if (token.isIdentifier()) {
+      token = parseQualified(token);
+    } else {
+      token = parseLiteralStringOrRecoverExpression(token);
+    }
     Token semicolon = token;
     token = expect(';', token);
     listener.endPartOf(partKeyword, semicolon);
     return token;
   }
 
   Token parseMetadataStar(Token token, {bool forParameter: false}) {
     listener.beginMetadataStar(token);
     int count = 0;
     while (optional('@', token)) {
@@ skipping 2663 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }