Refactor post requests, implement bot cancel/terminate

appengine/swarming/elements/res/js/common.js

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 this.swarming = this.swarming || function() {
 
   var swarming = {};
 
   swarming.stableSort = function(arr, comp) {
     if (!arr || !comp) {
@@ skipping 32 matching lines @@
   swarming.naturalCompare = function(a, b) {
     // Try numeric, aka "natural" sort and use it if ns is not NaN.
     // Javascript will try to corece these to numbers or return NaN.
     var ns = a - b;
     if (!isNaN(ns)) {
       return ns;
     }
     return String(a).localeCompare(b);
   };
 
+  // postWithToast makes a post request and updates the error-toast
+  // element with the response, regardless of failure.  See error-toast.html
+  // for more information.
+  swarming.postWithToast = function(url, msg, auth_headers) {
+    // Keep toast displayed until we hear back from the request.
+    sk.errorMessage(msg, 0);
+
+    sk.request("POST", url, undefined, auth_headers).then(function(response) {
+      sk.errorMessage("Request sent.  Response: "+response, 3000);
+    }).catch(function(reason) {
+      console.log("Request failed", reason);
+      sk.errorMessage("Request failed.  Reason: "+reason, 5000);
+    });
+  }
+
   return swarming;
 }();