Introduce new bot-page UI

appengine/swarming/elements/res/imp/botpage/bot-page-shared-behavior.html

+<!--
+  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.
+
+  window.SwarmingBehaviors.BotPageBehavior contains any shared functions and
+  constants used by the bot-page and its sub-elements.
+
+  To use it, include
+      behaviors: [SwarmingBehaviors.BotPageBehavior]
+  in the creation of your Polymer element.
+-->
+<link rel="import" href="/res/imp/common/common-behavior.html">
+<script>
+  (function(){
+
+
+    // This behavior wraps up all the shared bot-page functionality by
+    // extending SwarmingBehaviors.CommonBehavior
+    SwarmingBehaviors.BotPageBehavior = [SwarmingBehaviors.CommonBehavior, {
+
+      // timeDiffApprox returns the approximate difference between now and
+      // the specified date.
+      _timeDiffApprox: function(date){
+        if (!date) {
+          return "eons";
+        }
+        return sk.human.diffDate(date.getTime());
+      },
+
+      // timeDiffExact returns the exact difference between the two specified
+      // dates.  E.g. 2d 22h 22m 28s ago If a second date is not provided,
+      // now is used.
+      _timeDiffExact: function(first, second){
+        if (!first) {
+          return "eons";
+        }
+        if (!second) {
+          second = new Date();
+        }
+        return sk.human.strDuration((second.getTime() - first.getTime())/1000);
+      },
+
+    }];
+  })()
+</script>