[MD History] Add routing to the synced devices page.

chrome/browser/resources/md_history/app.js

Index: chrome/browser/resources/md_history/app.js
diff --git a/chrome/browser/resources/md_history/app.js b/chrome/browser/resources/md_history/app.js
index 6d3f5d4e2d111d016111463a05fa1550b1bec366..6475b13e9afb5779c1c5871389d56cd6e0ad5512 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -44,8 +44,18 @@ Polymer({
         };
       }
     },
+
+    // Route data for the current page.
+    routeData_: Object,
   },
 
+  observers: [
+    // routeData_.page <=> selectedPage
+    'routeDataChanged_(routeData_.page)',
+    'selectedPageChanged_(selectedPage_)',
+  ],
+
+  // TODO(calamity): Replace these event listeners with data bound properties.
   listeners: {
     'cr-menu-tap': 'onMenuTap_',
     'history-checkbox-select': 'checkboxSelected',
@@ -159,7 +169,7 @@ Polymer({
    * @private
    */
   syncedTabsSelected_: function(selectedPage) {
-    return selectedPage == 'synced-devices';
+    return selectedPage == 'syncedTabs';
   },
 
   /**
@@ -173,4 +183,30 @@ Polymer({
   shouldShowSpinner_: function(querying, incremental, searchTerm) {
     return querying && !incremental && searchTerm != '';
   },
+
+  /**
+   * @param {string} page
+   * @private
+   */
+  routeDataChanged_: function(page) {
+    this.selectedPage_ = page;
+  },
+
+  /**
+   * @param {string} selectedPage
+   * @private
+   */
+  selectedPageChanged_: function(selectedPage) {
+    this.set('routeData_.page', selectedPage);
+  },
+
+  /**
+   * @param {string} selectedPage
+   * @param {Array} items
+   * @return {string}
+   * @private
+   */
+  getSelectedPage_(selectedPage, items) {

[tsergeant, 2016/07/13 07:23:33]

If I understand correctly, this only exists to force the selection to
re-evaluate after the synced device manager is created.

That's fairly subtle behavior, so it would be nice to document it.

[calamity, 2016/07/14 06:20:57]

Good point. Done.

+    return selectedPage;
+  },
 });