Rework the replay test to be more correct

pkg/analysis_server/test/stress/utilities/logger.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * A utility class used to write logging information during a test.
+ */
+class Logger {
+  /**
+   * The width of the field in which labels are printed.
+   */
+  static const int _labelWidth = 8;
+
+  /**
+   * The separator used to separate the label from the content.
+   */
+  static const String _separator = ' : ';
+
+  /**
+   * The sink to which the logged information should be written.
+   */
+  final StringSink sink;
+
+  /**
+   * Initialize a newly created logger to write to the given [sink].
+   */
+  Logger(this.sink);
+
+  /**
+   * Log the given information.
+   *
+   * The [label] is used to indicate the kind of information being logged, while
+   * the [content] contains the actual information. If a list of [arguments] is
+   * provided, then they will be written after the content.
+   */
+  void log(String label, String content, {List<String> arguments = null}) {
+    for (int i = _labelWidth - label.length; i > 0; i--) {
+      sink.write(' ');
+    }
+    sink.write(label);
+    sink.write(_separator);
+    sink.write(content);
+    arguments?.forEach((String argument) {
+      sink.write(' ');
+      sink.write(argument);
+    });
+    sink.writeln();
+  }
+}