Add test to compare-failures

tools/gardening/lib/src/buildbot_structures.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.
 
 import 'util.dart';
 
 /// The [Uri] of a build step stdio log split into its subparts.
 class BuildUri {
   final String scheme;
   final String host;
@@ skipping 148 matching lines @@
   final String actual;
   final String text;
 
   factory TestFailure(BuildUri uri, List<String> lines) {
     List<String> parts = split(lines.first, ['FAILED: ', ' ', ' ']);
     String configName = parts[1];
     String archName = parts[2];
     String testName = parts[3];
     TestConfiguration id =
         new TestConfiguration(configName, archName, testName);
-    String expected = split(lines[1], ['Expected: '])[1];
-    String actual = split(lines[2], ['Actual: '])[1];
+    String expected = split(lines[1], ['Expected: '])[1].trim();
+    String actual = split(lines[2], ['Actual: '])[1].trim();
     return new TestFailure.internal(
         uri, id, expected, actual, lines.skip(3).join('\n'));
   }
 
   TestFailure.internal(
       this.uri, this.id, this.expected, this.actual, this.text);
 
   String toString() {
     StringBuffer sb = new StringBuffer();
     sb.write('FAILED: $id\n');
@@ skipping 40 matching lines @@
 
 /// The result of a single test for a single test step.
 class TestStatus {
   final TestConfiguration config;
   final String status;
 
   TestStatus(this.config, this.status);
 
   String toString() => '$config: $status';
 }