Add failed_once category to Sheriff-O-Matic.

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(failures, commitList) {
@@ skipping 29 matching lines @@
   return this._annotate({
     bug: undefined,
   });
 };
 
 CTFailureGroup.prototype._computeProperties = function() {
   this.isSnoozed = Date.now() < this._annotation.snoozeTime;
   if (this.isSnoozed) {
     this.category = 'snoozed';
   } else {
+    var totalFailures = 0;
+    this.failures.map(function(f) {

[ojan, 2014/09/05 18:39:44]

In the common case, this is going to do a ton of work that it doesn't need to.
As soon as the totalFailures is > 1, we can bail out of both loops. How about
writing this as helper function (e.g. _failedOnce) that does a nested for loop
and early returns a boolean?

This is on my mind because we recently had 7600 failures on tip of tree and
sheriff-o-matic basically became unusable due to excessive, unnecessary looping.
:(

+      var resultNodes = f.resultNodesByBuilder;
+      Object.keys(resultNodes, function(r) {
+        totalFailures += resultNodes[r].failingBuildCount;
+      }.bind(this));
+    });
+    if (totalFailures == 1) {
+      this.category = 'failed_once';

[ojan, 2014/09/05 18:39:44]

Nit: We don't have many cases of string values like this, so there's no standard
practice exactly, but I slightly lean towards camelcase (i.e. failedOnce).

+    } else {
+      this.category = 'default';
+    }
     // FIXME: crbug.com/400397 Split into: Whole step failure, Tree closer, Test failure, Flaky tests
-    this.category = 'default';
   }
 
   this.bug = this._annotation.bug;
   // FIXME: Bug labels would be simpler to implement as a filter in the UI.
   if (this.bug != null)
     this.bugLabel = 'Bug ' + /([0-9]{3,})/.exec(this.bug)[0];
   else
     this.bugLabel = undefined;
 };
 
@@ skipping 51 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>