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

BUG=https://code.google.com/p/dart/issues/detail?id=9294,https://code.google.com/p/dart/issues/detail?id=9295
R=sgjesse@google.com

Review URL: https://codereview.chromium.org//17261026

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@24262 260f80e4-7a28-3924-810f-c04153c831b5

lib/src/io.dart

@@ -591,19 +591,12 @@ Future _doProcess(Function fn, String executable, List<String> args,
     executable = "cmd";
   }
 
-  var env = null;
-  if (environment != null) {
-    env = new Map.from(Platform.environment);
-    environment.forEach((key, value) => env[key] = value);
-  }
-
-
   log.process(executable, args);
 
   return fn(executable,
             args,
             workingDirectory: workingDir,
-            environment: env);
+            environment: environment);
 }
 
 /// Wraps [input] to provide a timeout. If [input] completes before

test/test_pub.dart

@@ -453,8 +453,7 @@ ScheduledProcess startPub({List args, Future<Uri> tokenEndpoint}) {
 
   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);