Some perf improvements to sheriff-o-matics updates.

Tools/GardeningServer/model/ct-failure-group.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.
 -->
 
 <link rel="import" href="ct-commit-list.html">
 
 <script>
 function CTFailureGroup(key, data) {
@@ skipping 27 matching lines @@
   });
 };
 
 CTFailureGroup.prototype.clearBug = function(bug) {
   return this._annotate({
     bug: undefined,
   });
 };
 
 CTFailureGroup.prototype._failedOnce = function() {
-  var totalFailures = 0;
-  for (var i = 0; i < this.data.dataToExamine().length; i++) {
-    var resultNodes = this.data.dataToExamine()[i].resultNodesByBuilder;
-    Object.keys(resultNodes, function(r) {
-      totalFailures += resultNodes[r].failingBuildCount;
-      if (totalFailures > 1)
-        return false;
-    }.bind(this));
-  }
-  return totalFailures == 1;
+  return this.data.failedOnce && this.data.failedOnce();
 }
 
 CTFailureGroup.prototype._computeProperties = function() {
   this.isSnoozed = Date.now() < this._annotation.snoozeTime;
   if (this.isSnoozed) {
     this.category = 'snoozed';
   } else {
     if (this._failedOnce()) {
       this.category = 'failedOnce';
     } else {
@@ skipping 58 matching lines @@
   }.bind(this));
 };
 
 CTFailureGroup.fetchAnnotations = function() {
   // FIXME: Fetch annotations from frontend.
   var stored = localStorage.CTFailureGroupAnnotations;
   var annotations = stored ? JSON.parse(stored) : {};
   return Promise.resolve(annotations);
 };
 </script>