Group similar failures (same directory, same fixture)

Tools/GardeningServer/model/ct-failure.html

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <script>
 function CTFailure(step, reason, resultsByBuilder, firstFailingRevisions, lastPassingRevisions) {
   this.step = step;
   // FIXME: Rename this to reason.
@@ skipping 25 matching lines @@
     treeToDashboardGroup[tree] + '&' +
     Object.toQueryString({
       tests: this.testName,
       testType: testType,
     });
 }
 
 CTFailure.prototype.embeddedFlakinessDashboardURL = function(tree) {
   return this.flakinessDashboardURL(tree) + '&showChrome=false';
 }
+
+CTFailure.prototype.reasonGroupName = function() {
+  if (!this.testName)
+    return undefined;
+  if (this.step == 'webkit_tests')
+    return this.testName.substr(0, this.testName.lastIndexOf('/'));
+  return this.testName.substr(0, this.testName.lastIndexOf('.'));
+};
 </script>