dart:platform | Remove isWindows, isLinux, isAndroid, isMacOS from dart:platform.

tests/lib/platform/uri_test.dart

Index: tests/lib/platform/uri_test.dart
diff --git a/tests/lib/platform/uri_test.dart b/tests/lib/platform/uri_test.dart
index 7aaf8e0724a6e16a1d780e4d8675cbdda8f17c73..bca7b6d33b4bc7929803ddc51d98a0a3ee9ba433 100644
--- a/tests/lib/platform/uri_test.dart
+++ b/tests/lib/platform/uri_test.dart
@@ -6,7 +6,7 @@ import "package:expect/expect.dart";
 import "dart:platform" as platform;
 
 main() {
-  if (platform.isWindows) {
+  if (platform.operatingSystem == 'windows') {
     Expect.equals("a\\b", Uri.parse("a/b").toFilePath());
     Expect.equals("a\\b\\", Uri.parse("a/b/").toFilePath());
     Expect.equals("a b", Uri.parse("a%20b").toFilePath());