Support passing an environment variable map to child processes.

tests/standalone/src/io/ProcessEnvironmentTest.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:io');
+#import('dart:isolate');
+#source('ProcessTestUtil.dart');
+
+runEnvironmentProcess(Map environment, name, callback) {
+  var dartExecutable = getDartFileName();
+  var options = new ProcessOptions();
+  options.environment = environment;
+  var printEnv = 'tests/standalone/src/io/PrintEnv.dart';
+  if (!new File(printEnv).existsSync()) {
+    printEnv = '../$printEnv';
+  }
+  var process = new Process.run(dartExecutable,
+                                [printEnv, name],
+                                options,
+                                (exit, out, err) {
+    Expect.equals(0, exit);
+    callback(out);
+  });
+  process.onError = (e) => Expect.fail('Unexpected process start error');
+}
+
+testEnvironment() {
+  var donePort = new ReceivePort();
+  Map env = Platform.environment();
+  Expect.isFalse(env.isEmpty());
+  // Check that some value in the environment stays the same when passed
+  // to another process.
+  for (var k in env.getKeys()) {
+    runEnvironmentProcess(env, k, (output) {
+      // Only check startsWith. The print statements will add
+      // newlines at the end.
+      Expect.isTrue(output.startsWith(env[k]));
+      // Add a new variable and check that it becomes an environment
+      // variable in the child process.
+      var copy = new Map.from(env);
+      var name = 'MYENVVAR';
+      while (env.containsKey(name)) name = '${name}_';
+      copy[name] = 'value';
+      runEnvironmentProcess(copy, name, (output) {
+        Expect.isTrue(output.startsWith('value'));
+        donePort.close();
+      });
+    });
+    // Only check one value to not spin up too many processes testing the
+    // same things.
+    break;
+  }
+}
+
+main() {
+  testEnvironment();
+}