Adds a snooze button to the sheriff-o-matic ui

Tools/GardeningServer/ui/ct-failure-stream.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="../bower_components/core-collapse/core-collapse.html">
+<link rel="import" href="../bower_components/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="ct-failure-card.html">
 
 <polymer-element name="ct-failure-stream" attributes="groups commits tree" noscript>
   <template>
     <style>
       :host {
         display: block;
       }
 
       ct-failure-card {
         margin: 5px;
         padding: 5px;
         border-top: 1px solid lightgrey;
       }
     </style>
-    <template repeat="{{failures in groups}}">
-      <ct-failure-card failures="{{ failures }}" commits="{{ commits }}" tree="{{ tree }}"></ct-failure-card>
+    Show snoozed failures: <paper-toggle-button checked="{{ showSnoozed }}"></paper-toggle-button>

[ojan, 2014/08/06 04:03:01]

We should only show this if there are any snoozed failures. And lets put the
snoozed failures below the non-snoozed failures since they're theoretically the
failures the sheriff doesn't need to be thinking about.

I also had another idea. I can't decide if it's a good one or not. It's related
to crbug.com/400397. Instead of collapsing snoozed failures we could give them a
dedicated ct-failure-stream at the bottom. The advantage of that is that we
don't need to do any collapsing behavior and it doesn't take up any precious UI
space when there are non-snoozed failures to fix. The disadvantage is that we'd
have to clump together the snoozed tree closers, reliable failures and flaky
failures in the snoozing failure stream.

I slightly lean toward the latter approach. If you're OK with implementing it,
I'd like to give that a try first and only come back to this collapsing thing if
we decide the other UI doesn't work. WDYT?

In terms of how this would be implemented, what I pictured is that
ct-failure-analyzer, instead of having one flat list of failures, would have a
list of failures for each ct-failure-stream.

[dstockwell, 2014/08/06 06:55:13]

I've left them in the stream (but dimmed) for this patch, let's split them out
into a separate stream in another patch.

+    <core-collapse opened="{{showSnoozed}}" duration="0.3">
+      <template repeat="{{ group in groups }}">
+        <template if="{{ group.isSnoozed }}">
+          <ct-failure-card group="{{ group }}" commits="{{ commits }}" tree="{{ tree }}"></ct-failure-card>
+        </template>
+      </template>
+    </core-collapse>
+
+    <template repeat="{{ group in groups }}">
+      <template if="{{ !group.isSnoozed }}">
+        <ct-failure-card group="{{ group }}" commits="{{ commits }}" tree="{{ tree }}"></ct-failure-card>
+      </template>
     </template>
   </template>
 </polymer-element>