Include parent environment by default, add option to not, for Process.

sdk/lib/_internal/pub/test/test_pub.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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 435 matching lines @@
 
   // Find the main pub entrypoint.
   var pubPath = path.join(testDirectory, '..', 'bin', 'pub.dart');
 
   var dartArgs = ['--package-root=$_packageRoot/', '--checked', pubPath,
       '--verbose'];
   dartArgs.addAll(args);
 
   if (tokenEndpoint == null) tokenEndpoint = new Future.value();
   var environmentFuture = tokenEndpoint.then((tokenEndpoint) {
-    // TODO(nweiz): remove this when issue 9294 is fixed.
-    var environment = new Map.from(Platform.environment);
+    var environment = {};
     environment['_PUB_TESTING'] = 'true';
     environment['PUB_CACHE'] = pathInSandbox(cachePath);
     environment['DART_SDK'] = pathInSandbox(sdkPath);
     if (tokenEndpoint != null) {
       environment['_PUB_TEST_TOKEN_ENDPOINT'] =
         tokenEndpoint.toString();
     }
     return environment;
   });
 
@@ skipping 327 matching lines @@
   bool matches(item, Map matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }