Properly detect whether we're running on a buildbot.

BUILDBOT_BUILDERNAME is only set for bots using annotated steps, which
isn't all of them. This detects whether the username is "chrome-bot"
instead.

This check is currently only being used to decide whether to use
unittest's compact VM config or the default config.

R=rnystrom@google.com, sigmund@google.com

Review URL: https://codereview.chromium.org//58933006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/unittest@30206 260f80e4-7a28-3924-810f-c04153c831b5

lib/compact_vm_config.dart

@@ -190,7 +190,7 @@ class CompactVMConfiguration extends VMConfiguration {
 void useCompactVMConfiguration() {
   // If the test is running on the Dart buildbots, we don't want to use this
   // config since it's output may not be what the bots expect.
-  if (Platform.environment.containsKey('BUILDBOT_BUILDERNAME')) {
+  if (Platform.environment['LOGNAME'] == 'chrome-bot') {
     return;
   }