Update Windows file implementation to use the unicode APIs.

tests/standalone/io/file_error_test.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.
 //
 // Dart test program for testing error handling in file I/O.
 
 #import("dart:io");
 #import("dart:isolate");
 
 Directory tempDir() {
   return new Directory('').createTempSync();
 }
 
 
 bool checkNonExistentFileException(e, str) {
   Expect.isTrue(e is FileIOException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(e.toString().indexOf(str) != -1);
-  if (Platform.operatingSystem == "linux") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "macos") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "windows") {
-    Expect.isTrue(
-        e.toString().indexOf(
-            "The system cannot find the file specified") != -1);
-  }
   // File not not found has error code 2 on all supported platforms.
   Expect.equals(2, e.osError.errorCode);
-
   return true;
 }
 
 
 bool checkOpenNonExistentFileException(e) {
   return checkNonExistentFileException(e, "Cannot open file");
 }
 
 
 bool checkDeleteNonExistentFileException(e) {
@@ skipping 73 matching lines @@
     return true;
   });
 }
 
 
 bool checkCreateInNonExistentDirectoryException(e) {
   Expect.isTrue(e is FileIOException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(e.toString().indexOf("Cannot create file") != -1);
   if (Platform.operatingSystem == "linux") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
     Expect.equals(2, e.osError.errorCode);
   } else if (Platform.operatingSystem == "macos") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
     Expect.equals(2, e.osError.errorCode);
   } else if (Platform.operatingSystem == "windows") {
-    Expect.isTrue(
-        e.toString().indexOf(
-            "The system cannot find the path specified") != -1);
     Expect.equals(3, e.osError.errorCode);
   }
 
   return true;
 }
 
 void testCreateInNonExistentDirectory() {
   Directory temp = tempDir();
   ReceivePort p = new ReceivePort();
   p.receive((x, y) {
@@ skipping 12 matching lines @@
     checkCreateInNonExistentDirectoryException(e);
     p.toSendPort().send(null);
     return true;
   });
 }
 
 bool checkFullPathOnNonExistentDirectoryException(e) {
   Expect.isTrue(e is FileIOException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(e.toString().indexOf("Cannot retrieve full path") != -1);
-  if (Platform.operatingSystem == "linux") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "macos") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "windows") {
-    Expect.isTrue(
-        e.toString().indexOf(
-            "The system cannot find the file specified") != -1);
-  }
   // File not not found has error code 2 on all supported platforms.
   Expect.equals(2, e.osError.errorCode);
 
   return true;
 }
 
 void testFullPathOnNonExistentDirectory() {
   Directory temp = tempDir();
   ReceivePort p = new ReceivePort();
   p.receive((x, y) {
@@ skipping 13 matching lines @@
     p.toSendPort().send(null);
     return true;
   });
 }
 
 bool checkDirectoryInNonExistentDirectoryException(e) {
   Expect.isTrue(e is FileIOException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(
       e.toString().indexOf("Cannot retrieve directory for file") != -1);
-  if (Platform.operatingSystem == "linux") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "macos") {
-    Expect.isTrue(e.toString().indexOf("No such file or directory") != -1);
-  } else if (Platform.operatingSystem == "windows") {
-    Expect.isTrue(
-        e.toString().indexOf(
-            "The system cannot find the file specified") != -1);
-  }
   // File not not found has error code 2 on all supported platforms.
   Expect.equals(2, e.osError.errorCode);
 
   return true;
 }
 
 void testDirectoryInNonExistentDirectory() {
   Directory temp = tempDir();
   ReceivePort p = new ReceivePort();
   p.receive((x, y) {
@@ skipping 284 matching lines @@
   testReadAsBytesNonExistent();
   testReadAsTextNonExistent();
   testReadAsLinesNonExistent();
   testWriteByteToReadOnlyFile();
   testWriteListToReadOnlyFile();
   testTruncateReadOnlyFile();
   testOperateOnClosedFile();
   testRepeatedlyCloseFile();
   testRepeatedlyCloseFileSync();
 }