Non-Local Join for Media Router and Presentation API

chrome/browser/resources/media_router/elements/route_details/route_details.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">

[apacible, 2015/12/09 19:56:25]

What's the advantage of using iron-flex-layout rather than flexbox?

Since we're also adding a new import, please note performance differences
before/after your changes. Usually we check mean/median of 5-10 runs in
chrome://tracing.

Steps:
1. Press "Record" and select the Media Router option. Everything else can be
unchecked. Start recording.
2. Open the Media Router dialog (can be in new tab).
3. Stop recording.
4. Check the "MR UI" block for load time.

[matt.boetger, 2015/12/16 00:21:08]

I had originally used flexbox, but after one of my syncs to use the latest code
- that stopped working, so I had put in the iron-flex-layout. It seems to be
working again, so I'll remove the iron-flex-layout.

 <dom-module id="route-details">
   <link rel="import" type="css" href="../../media_router_common.css">
   <link rel="import" type="css" href="route_details.css">
   <template>
     <div id="route-information" hidden$="[[!isCustomControllerHidden_]]">
       <span>[[activityStatus_]]</span>
     </div>
     <extensionview id="custom-controller"
         hidden$="[[isCustomControllerHidden_]]">
     </extensionview>
-    <paper-button raised id="close-route-button" class="button"
-        on-click="closeRoute_">
-      <span>[[stopCastingButtonText_]]</span>
-    </paper-button>
+    <div class="flex-button-container">
+      <paper-button raised class="route-button button"
+          id="join-route-button"
+          hidden$="[[!route.canJoin]]"
+          on-click="joinRoute_">
+        <span>[[joinButtonText_]]</span>
+      </paper-button>
+      <paper-button raised class="route-button button"
+          id="close-route-button"
+          on-click="closeRoute_">
+        <span>[[stopCastingButtonText_]]</span>
+      </paper-button>
+    <div>
   </template>
 <script src="route_details.js"></script>
 </dom-module>