Move commit list out its own model.

Tools/GardeningServer/ui/ct-failure-card.html

Index: Tools/GardeningServer/ui/ct-failure-card.html
diff --git a/Tools/GardeningServer/ui/ct-failure-card.html b/Tools/GardeningServer/ui/ct-failure-card.html
index 7bf9f799d6ce025670efbd5dec89bfcb397478e8..97c50ae576a6070f4f2452c90efce3f498ddafed 100644
--- a/Tools/GardeningServer/ui/ct-failure-card.html
+++ b/Tools/GardeningServer/ui/ct-failure-card.html
@@ -8,7 +8,7 @@ found in the LICENSE file.
 <link rel="import" href="ct-commit-list.html">
 <link rel="import" href="ct-test-list.html">
 
-<polymer-element name="ct-failure-card" attributes="group commits tree">
+<polymer-element name="ct-failure-card" attributes="group commitList tree">
   <template>
     <style>
       :host {
@@ -63,9 +63,7 @@ found in the LICENSE file.
     <ct-builder-grid failures="{{ group.failures }}"></ct-builder-grid>
     <div class="{{ { failure: true, snoozed: group.isSnoozed } | tokenList }}">
       <ct-test-list tests="{{ group.failures }}" tree="{{ tree }}"></ct-test-list>
-      <ct-commit-list first="{{ group.failures[0].lastPassingRevisions }}"
-          last="{{ group.failures[0].firstFailingRevisions }}"
-          commits="{{ commits }}"></ct-commit-list>
+      <ct-commit-list commitList="{{ commitList }}"></ct-commit-list>
     </div>
     <paper-button id="examine" on-tap="{{ examine }}">Examine</paper-button>
     <template if="{{ !group.isSnoozed }}">
@@ -78,7 +76,7 @@ found in the LICENSE file.
   <script>
     Polymer({
       group: null,
-      commits: {},
+      commitList: null,
       tree: '',
 
       examine: function() {