Make standalone tests not dependent on current working directory.

tests/standalone/io/file_input_stream_test.dart

Index: tests/standalone/io/file_input_stream_test.dart
diff --git a/tests/standalone/io/file_input_stream_test.dart b/tests/standalone/io/file_input_stream_test.dart
index 86cb355aa403dadd83db57e8cb19528e53babeff..25cf360cb19fd3b567c846bec13ff0f96127ffaf 100644
--- a/tests/standalone/io/file_input_stream_test.dart
+++ b/tests/standalone/io/file_input_stream_test.dart
@@ -11,8 +11,12 @@ import "package:expect/expect.dart";
 
 // Helper method to be able to run the test from the runtime
 // directory, or the top directory.
-String getFilename(String path) =>
-    new File(path).existsSync() ? path : '../$path';
+String getFilename(String path) {
+  var testPath = Platform.script.resolve('../../../$path');
+  return new File.fromUri(testPath).existsSync()
+      ? testPath.toFilePath()
+      : Platform.script.resolve('../../../runtime/$path').toFilePath();
+}
 
 void testStringLineSplitter() {
   String fileName = getFilename("tests/standalone/io/readuntil_test.dat");