Add cost to task page

appengine/swarming/ui/res/imp/taskpage/task-page.html

Index: appengine/swarming/ui/res/imp/taskpage/task-page.html
diff --git a/appengine/swarming/ui/res/imp/taskpage/task-page.html b/appengine/swarming/ui/res/imp/taskpage/task-page.html
index ff3b320b5e94925a7133e997f32d3e6dc01ba489..3a042a58ffc650bd456cca1c0c39751762de6912 100644
--- a/appengine/swarming/ui/res/imp/taskpage/task-page.html
+++ b/appengine/swarming/ui/res/imp/taskpage/task-page.html
@@ -491,6 +491,10 @@
                   <td class$="[[_internalClass(_result.internal_failure)]]">[[_result.internal_failure]]</td>
                 </tr>
                 <tr>
+                  <td>Cost (USD)</td>
+                  <td>$[[_cost(_result)]]</td>
+                </tr>
+                <tr>
                   <td>Isolated Outputs</td>
                   <td>
                     <a href$="[[_isolateLink(_result.outputs_ref)]]">
@@ -801,6 +805,13 @@
         return args.join(" ");
       },
 
+      _cost: function(result) {
+        if (!result || !result.costs_usd || !result.costs_usd.length) {
+          return 0;
+        }
+        return result.costs_usd[0].toFixed(4);
+      },
+
       _disambiguate: function(taskId, result) {
         if (!taskId.endsWith("0") || !result) {
           return false;