Show bootstrap and server bot_code version

appengine/swarming/elements/res/imp/index/swarming-index.html

Index: appengine/swarming/elements/res/imp/index/swarming-index.html
diff --git a/appengine/swarming/elements/res/imp/index/swarming-index.html b/appengine/swarming/elements/res/imp/index/swarming-index.html
index 5370895b7cf84cf0cfa655f116104a0187087b0c..c9e050967ced70e0b208d5ca5edb5d36f5bbd2ac 100644
--- a/appengine/swarming/elements/res/imp/index/swarming-index.html
+++ b/appengine/swarming/elements/res/imp/index/swarming-index.html
@@ -47,7 +47,7 @@
 
     <swarming-app
       client_id="[[client_id]]"
-      auth_headers="{{auth_headers}}"
+      auth_headers="{{_auth_headers}}"
       permissions="{{_permissions}}"
       server_version="{{_server_version}}"
       name="Swarming Server"
@@ -55,6 +55,7 @@
 
       <h2>Service Status</h2>
       <div>Server Version: [[_server_version.server_version]]</div>
+      <div>Bot Version: [[_server_version.bot_version]]</div>
       <ul>
         <li>
           <!-- TODO(kjlubick) convert these linked pages to Polymer-->
@@ -132,10 +133,13 @@
           type: String,
         },
 
+
+        _auth_headers: {
+          type: String,
+        },
         _bootstrap_token: {
           type: String,
-          // TODO(kjlubick): fetch this from an API
-          value: "abc123",
+          value: "...",
         },
         _busy: {
           type: Boolean,
@@ -162,11 +166,25 @@
         },
       },
 
+      observers: ["_fetchBootstrap(_permissions,_auth_headers)"],
+
 
       _cannotBootstrap: function(permissions) {
         return !(permissions && permissions.get_bootstrap_token);
       },
 
+      _fetchBootstrap: function(permissions, auth_headers) {
+        if (!auth_headers || !permissions || this._cannotBootstrap(permissions)) {
+          return;
+        }
+        var p = sk.request("POST", "/_ah/api/swarming/v1/server/token", undefined, auth_headers);

[stephana, 2016/09/26 20:04:11]

Shouldn't this also deal with the case when the POST request fails. 
IMO the pattern:

... 
this.set("_busy", true); 
sk.request("POST" ...).then(JSON.parse).then(function(t) {
....
  this.set("_busy", false); 
}.bind(this).catch(function(err) {
  this.set("_busy", false); 
  errorHandler(err);
}.bind(this); 
...

would be preferable. 

[kjlubick, 2016/09/27 12:09:31]

Done.

+        this.set("_busy", true);
+        p.then(JSON.parse).then(function(t){
+          this.set("_bootstrap_token", t.bootstrap_token);
+          this.set("_busy", false);
+        }.bind(this))
+      },
+
       _makeInstancesUrl: function(details, project_id) {
         return "https://console.cloud.google.com/appengine/instances?project="+
             project_id+"&versionId="+details.server_version;