Drop support for old SDK and shelf versions.

test/io.dart

 // Copyright (c) 2015, 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 test.test.io;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_process.dart';
 import 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:test/src/util/io.dart';
 
 /// The path to the root directory of the `test` package.
 final String packageDir = p.dirname(p.dirname(libraryPath(#test.test.io)));
 
 /// The path to the `pub` executable in the current Dart SDK.
 final _pubPath = p.absolute(p.join(
-    p.dirname(Platform.executable),
+    p.dirname(Platform.resolvedExecutable),
     Platform.isWindows ? 'pub.bat' : 'pub'));
 
 /// The platform-specific message emitted when a nonexistent file is loaded.
 final String noSuchFileMessage = Platform.isWindows
     ? "The system cannot find the file specified."
     : "No such file or directory";
 
 /// A regular expression that matches the output of "pub serve".
 final _servingRegExp =
     new RegExp(r'^Serving myapp [a-z]+ on http://localhost:(\d+)$');
@@ skipping 87 matching lines @@
     String description}) {
   var allArgs = Platform.executableArguments.map((arg) {
     // The package root might be relative, so we need to make it absolute if
     // we're going to run in a different working directory.
     if (!arg.startsWith("--package-root=")) return arg;
     return "--package-root=" +
         p.absolute(p.fromUri(arg.substring("--package-root=".length)));
   }).toList()..addAll(args);
 
   return new ScheduledProcess.start(
-      p.absolute(Platform.executable), allArgs,
+      p.absolute(Platform.resolvedExecutable), allArgs,
       workingDirectory: _sandbox,
       environment: environment,
       description: description);
 }
 
 /// Runs Pub.
 ScheduledProcess runPub(List args, {Map<String, String> environment}) {
   return new ScheduledProcess.start(
       _pubPath, args,
       workingDirectory: _sandbox,
@@ skipping 19 matching lines @@
     var match;
     while (match == null) {
       var line = await pub.stdout.next();
       match = _servingRegExp.firstMatch(line);
     }
     _pubServePortCompleter.complete(int.parse(match[1]));
   }, "waiting for pub serve to emit its port number");
 
   return pub;
 }