Only remove 'PATH' from environment in process_environment_test.

tests/standalone/io/process_environment_test.dart

Index: tests/standalone/io/process_environment_test.dart
diff --git a/tests/standalone/io/process_environment_test.dart b/tests/standalone/io/process_environment_test.dart
index 5291751988a2fc3bff39cf689e85b0d6114c9774..cac9380e65da021fba314e2a95b7dadf0d92b07b 100644
--- a/tests/standalone/io/process_environment_test.dart
+++ b/tests/standalone/io/process_environment_test.dart
@@ -53,7 +53,10 @@ testEnvironment() {
 
 testNoIncludeEnvironment() {
   var donePort = new ReceivePort();
-  runEnvironmentProcess({}, "PATH", false, (output) {
+  var env = Platform.environment;
+  Expect.isTrue(env.containsKey('PATH'));
+  env.remove('PATH');
+  runEnvironmentProcess(env, "PATH", false, (output) {
     donePort.close();
     Expect.isTrue(output.startsWith("null"));
   });