Improve [relativize] for Windows.

dart/pkg/dartdoc/mirrors/dart2js_mirror.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('mirrors.dart2js');
 
 #import('../../../lib/compiler/compiler.dart', prefix: 'diagnostics');
 #import('../../../lib/compiler/implementation/elements/elements.dart');
 #import('../../../lib/compiler/implementation/apiimpl.dart', prefix: 'api');
 #import('../../../lib/compiler/implementation/scanner/scannerlib.dart');
@@ skipping 264 matching lines @@
   LibraryTypeCheckerTask(api.Compiler compiler) : super(compiler);
 
   void check(Node tree, TreeElements elements) {}
 }
 
 //------------------------------------------------------------------------------
 // Compilation implementation
 //------------------------------------------------------------------------------
 
 class Dart2JsCompilation implements Compilation {
+  bool isWindows = (Platform.operatingSystem == 'windows');
   api.Compiler _compiler;
   Uri cwd;
   bool isAborting = false;
   Map<String, SourceFile> sourceFiles;
 
   Future<String> provider(Uri uri) {
     if (uri.scheme != 'file') {
       throw new IllegalArgumentException(uri);
     }
     String source;
     try {
       source = readAll(uriPathToNative(uri.path));
     } on FileIOException catch (ex) {
-      throw 'Error: Cannot read "${relativize(cwd, uri)}" (${ex.osError}).';
+      throw 'Error: Cannot read "${relativize(cwd, uri, isWindows)}" '
+            '(${ex.osError}).';
     }
     sourceFiles[uri.toString()] =
-      new SourceFile(relativize(cwd, uri), source);
+      new SourceFile(relativize(cwd, uri, isWindows), source);
     return new Future.immediate(source);
   }
 
   void handler(Uri uri, int begin, int end,
                String message, diagnostics.Diagnostic kind) {
     if (isAborting) return;
     bool fatal =
         kind === diagnostics.Diagnostic.CRASH ||
         kind === diagnostics.Diagnostic.ERROR;
     if (uri === null) {
@@ skipping 1069 matching lines @@
     if (node !== null) {
       var span = system.compiler.spanFromNode(node, script.uri);
       return new Dart2JsLocation(script, span);
     } else {
       var span = system.compiler.spanFromElement(_variable);
       return new Dart2JsLocation(script, span);
     }
   }
 }