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.
   this.testName = reason;
   this.resultNodesByBuilder = resultsByBuilder;
   // FIXME: Move these up one layer to the groupedFailures object.
   this.firstFailingRevisions = firstFailingRevisions;
   this.lastPassingRevisions = lastPassingRevisions;
 }
+
+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>