[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 a16204324a4bf4384f0b4b5fb8b3d1c2846d2305..7bbe7eb2922a3882661960799e6659f7e3c04b5b 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -48,11 +48,23 @@ Polymer({
         };
       }
     },
+
+    // The top level route.
+    route: {
+      type: Object
+    },
+
+    // Route data for the current page.
+    routeData: {
+      type: Object,
+      observer: 'routeChanged_'
+    }
   },
 
   observers: [
     'searchTermChanged_(queryState_.searchTerm)',
     'groupedRangeChanged_(queryState_.range)',
+    'routeChanged_(route)',
   ],
 
   // TODO(calamity): Replace these event listeners with data bound properties.
@@ -68,6 +80,15 @@ Polymer({
     this.grouped_ = loadTimeData.getBoolean('groupByDomain');
   },
 
+  routeChanged_: function(route) {
+    var routeToElementId = {
+      'openTabs': 'history-synced-device-manager',
+    };

[tsergeant, 2016/06/08 03:42:17]

I'm not a big fan of this (as I think you predicted). What you're creating is a
1-1 mapping between two different types of strings, with a default:

openTabs <-> history-synced-device-manager
* --> history-list

Why not just use the string on the left (the user friendly page name)
everywhere, rather than using the string on the right in some places?

[calamity, 2016/06/14 05:05:50]

Ok, so we'll be going with /, /grouped/week, /grouped/month, /openTabs I guess?

+    var path = this.routeData.page;
+    var elementId = routeToElementId[path] || 'history-list';
+    this.selectedPage_ = elementId;
+  },
+
   /**
    * Listens for history-item being selected or deselected (through checkbox)
    * and changes the view of the top toolbar.