Move commit list out its own model.

Tools/GardeningServer/model/ct-failure-group.html

Index: Tools/GardeningServer/model/ct-failure-group.html
diff --git a/Tools/GardeningServer/model/ct-failure-group.html b/Tools/GardeningServer/model/ct-failure-group.html
index 470950c13b8c09a4c2f1394f9d9e460281ddbb73..bf6b63e8f2b38fe3e067e6b75fbafffcac6e652d 100644
--- a/Tools/GardeningServer/model/ct-failure-group.html
+++ b/Tools/GardeningServer/model/ct-failure-group.html
@@ -4,6 +4,8 @@ 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, failures, annotation) {
   this.key = key;
@@ -24,6 +26,10 @@ CTFailureGroup.prototype.unsnooze = function() {
   });
 };
 
+CTFailureGroup.prototype.commitList = function(commits) {
+  return new CTCommitList(this, commits);
+};
+
 CTFailureGroup.prototype._computeProperties = function() {
   this.isSnoozed = Date.now() < this.annotation.snoozeTime;
   if (this.isSnoozed) {