Remove dart:platform library.

tests/lib/platform/isolate_test.dart

-// Copyright (c) 2013, 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:platform" as platform;
-
-import "dart:isolate";
-import "package:unittest/unittest.dart";
-
-sendReceive(SendPort port, msg) {
-  var response = new ReceivePort();
-  port.send([msg, response.sendPort]);
-  return response.first;
-}
-
-main() {
-  test("platform in isolate", () {
-    var response = new ReceivePort();
-    Isolate.spawn(f, response.sendPort);
-    response.first.then(expectAsync1((sendPort) {
-      expect(sendReceive(sendPort, "platform.executable"),
-            completion(platform.executable));
-      if (platform.script != null) {
-        expect(sendReceive(sendPort, "platform.script").then((s) => s.path),
-              completion(endsWith('tests/lib/platform/isolate_test.dart')));
-      }
-      expect(sendReceive(sendPort, "platform.packageRoot"),
-            completion(platform.packageRoot));
-      expect(sendReceive(sendPort, "platform.executableArguments"),
-            completion(platform.executableArguments));
-    }));
-  });
-}
-
-void f(initialReplyTo) {
-  var port = new ReceivePort();
-  initialReplyTo.send(port.sendPort);
-  int count = 0;
-  port.listen((msg) {
-    var data = msg[0];
-    var replyTo = msg[1];
-    if (data == "platform.executable") {
-      replyTo.send(platform.executable);
-    }
-    if (data == "platform.script") {
-      replyTo.send(platform.script);
-    }
-    if (data == "platform.packageRoot") {
-      replyTo.send(platform.packageRoot);
-    }
-    if (data == "platform.executableArguments") {
-      replyTo.send(platform.executableArguments);
-    }
-    count++;
-    if (count == 4) {
-      port.close();
-    }
-  });
-}