Revert change to Platform.excutable and add Platform.resolvedExecutable

tests/standalone/io/platform_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.
 
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
 test() {
   Expect.isTrue(Platform.numberOfProcessors > 0);
   var os = Platform.operatingSystem;
   Expect.isTrue(os == "android" || os == "linux" || os == "macos" ||
       os == "windows");
   Expect.equals(Platform.isLinux, Platform.operatingSystem == "linux");
   Expect.equals(Platform.isMacOS, Platform.operatingSystem == "macos");
   Expect.equals(Platform.isWindows, Platform.operatingSystem == "windows");
   Expect.equals(Platform.isAndroid, Platform.operatingSystem == "android");
   var sep = Platform.pathSeparator;
   Expect.isTrue(sep == '/' || (os == 'windows' && sep == '\\'));
   var hostname = Platform.localHostname;
   Expect.isTrue(hostname is String && hostname != "");
   var environment = Platform.environment;
   Expect.isTrue(environment is Map<String, String>);
-  Expect.isTrue(Platform.executable.contains('dart'));
   if (!Platform.isWindows) {
-    Expect.isTrue(Platform.executable.startsWith('/'));
+    Expect.isTrue(Platform.executable.endsWith('dart'));
+    Expect.isTrue(Platform.resolvedExecutable.endsWith('dart'));
+  } else {
+    Expect.isTrue(Platform.executable.endsWith('dart.exe'));
+    Expect.isTrue(Platform.resolvedExecutable.endsWith('dart.exe'));
+  }
+  if (!Platform.isWindows) {
+    Expect.isTrue(Platform.resolvedExecutable.startsWith('/'));
   } else {
     // This assumes that tests (both locally and on the bots) are
     // running off a location referred to by a drive letter. If a UNC
     // location is used or long names ("\\?\" prefix) is used this
     // needs to be fixed.
     Expect.equals(Platform.executable.substring(1, 3), ':\\');
   }
   // Move directory to be sure script is correct.
   var oldDir = Directory.current;
   Directory.current = Directory.current.parent;
@@ skipping 86 matching lines @@
   Expect.throws(() => checkValidVersion('x.y.z'));
 }
 
 main() {
   // This tests assumes paths relative to dart main directory
   Directory.current = Platform.script.resolve('../../..').toFilePath();
   test();
   testIsolate();
   testVersion();
 }