MD History: Add routing for grouped history mode.

chrome/test/data/webui/md_history/md_history_browsertest.js

Index: chrome/test/data/webui/md_history/md_history_browsertest.js
diff --git a/chrome/test/data/webui/md_history/md_history_browsertest.js b/chrome/test/data/webui/md_history/md_history_browsertest.js
index d0a24cc1c2021b1d9148d919ea47630367ece951..a3d9a698fc683eb801ef4f173f00a3f666c4dd1c 100644
--- a/chrome/test/data/webui/md_history/md_history_browsertest.js
+++ b/chrome/test/data/webui/md_history/md_history_browsertest.js
@@ -173,7 +173,12 @@ function MaterialHistoryRoutingWithQueryParamTest() {}
 MaterialHistoryRoutingWithQueryParamTest.prototype = {
   __proto__: MaterialHistoryRoutingTest.prototype,
 
-  browsePreload: 'chrome://history?q=query',
+  browsePreload: 'chrome://history/history/week?q=query&offset=5',
+
+  commandLineSwitches:
+      MaterialHistoryBrowserTest.prototype.commandLineSwitches.concat([
+        {switchName: 'enable-grouped-history'}
+      ]),
 
   /** @override */
   setUp: function() {