Fix in testing scripts, decodeUtf8->encodeUtf8

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index 70edc804cc6702d37be9de8602e7e10f62dbf32c..aa84ae9cd637787c501b69c64bf22ee0642571e5 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -1320,7 +1320,7 @@ class BatchRunnerProcess {
         } else if (line.startsWith('>>> ')) {
           throw new Exception('Unexpected command from dartc batch runner.');
         } else {
-          buffer.addAll(decodeUtf8(line));
+          buffer.addAll(encodeUtf8(line));
           buffer.addAll("\n".charCodes);
         }
         line = stream.readLine();
@@ -1348,7 +1348,7 @@ class BatchRunnerProcess {
         if (line.startsWith('>>> EOF STDERR')) {
           _stderrDone();
         } else {
-          buffer.addAll(decodeUtf8(line));
+          buffer.addAll(encodeUtf8(line));
           buffer.addAll("\n".charCodes);
         }
         line = stream.readLine();