Remove hack for finding package-root in tests, now available in Platform

pkg/intl/test/message_extraction/message_extraction_test.dart

Index: pkg/intl/test/message_extraction/message_extraction_test.dart
diff --git a/pkg/intl/test/message_extraction/message_extraction_test.dart b/pkg/intl/test/message_extraction/message_extraction_test.dart
index 40c664e6accc87dad6fb87e2cfff2328a8d1c645..a040df1d5991b98841627d3af0ead43eab8b207e 100644
--- a/pkg/intl/test/message_extraction/message_extraction_test.dart
+++ b/pkg/intl/test/message_extraction/message_extraction_test.dart
@@ -12,37 +12,8 @@ import '../data_directory.dart';
 
 final dart = Platform.executable;
 
-// TODO(alanknight): We have no way of knowing what the package-root is,
-// so when we're running under the test framework, which sets the
-// package-root, we use a horrible hack and infer it from the executable.
-final packageDir = _findPackageDir(dart);
-
-/**
- * Find our package directory from the executable. If we seem to be running
- * from out/Release<arch>/dart or the equivalent Debug, then use the packages
- * directory under Release<arch>. Otherwise return null, indicating to use
- * the normal pub packages directory.
- */
-String _findPackageDir(executable) {
-  var oneUp = path.dirname(executable);
-  var tail = path.basename(oneUp);
-  // If we're running from test.dart, we want e.g. out/ReleaseIA32/packages
-  if (tail.contains('Release') || tail.contains('Debug')) {
-      return path.join(oneUp, 'packages/');
-  }
-  // Check for the case where we're running Release<arch>/dart-sdk/bin/dart
-  // (pub bots)
-  var threeUp = path.dirname(path.dirname(oneUp));
-  tail = path.basename(threeUp);
-  if (tail.contains('Release') || tail.contains('Debug')) {
-      return path.join(threeUp, 'packages/');
-  }
-  // Otherwise we will rely on the normal packages directory.
-  return null;
-}
-
-/** If our package root directory is set, return it as a VM argument. */
-final vmArgs = (packageDir == null) ? [] : ['--package-root=$packageDir'];
+/** The VM arguments we were given, most important package-root. */
+final vmArgs = Platform.executableArguments;
 
 /**
  * Translate a file path into this test directory, regardless of the