Expose the chromium waterfall in sheriff-o-matic.

Tools/GardeningServer/ui/ct-embedded-flakiness-dashboard-tests.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-embedded-flakiness-dashboard.html">
 
 <script>
 (function() {
 
 module("ct-embedded-flakiness-dashboard");
 
 asyncTest("url", 1, function() {
   var oldUrlForEmbeddedFlakinessDashboard = ui.urlForEmbeddedFlakinessDashboard;
   var reset = function() {
     ui.urlForEmbeddedFlakinessDashboard = oldUrlForEmbeddedFlakinessDashboard;
   }
 
   try {
-    ui.urlForEmbeddedFlakinessDashboard = function(test, step) { return "about:blank#" + test + step; }
+    ui.urlForEmbeddedFlakinessDashboard = function(test, step, tree) { return "about:blank#" + test + step + tree; }
     var embeddedFlakinessDashboard = document.createElement('ct-embedded-flakiness-dashboard');
     var testName = "foo/bar.html";
     var step = "foo_tests";
+    var tree = "blink";
     embeddedFlakinessDashboard.test = {
       testName: testName,
       step: step,
     };
+    embeddedFlakinessDashboard.tree = tree;
 
     requestAnimationFrame(function() {
       var iframe = embeddedFlakinessDashboard.shadowRoot.querySelector('#iframe');
-      equal(iframe.src, ui.urlForEmbeddedFlakinessDashboard(testName, step));
+      equal(iframe.src, ui.urlForEmbeddedFlakinessDashboard(testName, step, tree));
       reset();
       start();
     });
   } catch (e) {
     reset();
   }
 });
 
 asyncTest("heightChanged", 1, function() {
   var embeddedFlakinessDashboard = document.createElement('ct-embedded-flakiness-dashboard');
 
   function finishTest() {
     window.removeEventListener('message', finishTest);
     var iframe = embeddedFlakinessDashboard.shadowRoot.querySelector('#iframe');
     equal(iframe.style.height, "100px");
     start();
   }
   window.addEventListener('message', finishTest);
 
   requestAnimationFrame(function() {
     window.postMessage({command: 'heightChanged', height: "100"}, '*');
   });
 });
 
 })()
-</script>
+</script>