[MD History] Fix toolbar dates in grouped mode.

chrome/browser/resources/md_history/grouped_list.js

Index: chrome/browser/resources/md_history/grouped_list.js
diff --git a/chrome/browser/resources/md_history/grouped_list.js b/chrome/browser/resources/md_history/grouped_list.js
index a867d17f1815ebe5ed9895cedaa3240bfb1d23ca..f1664bf8b7d4fe2db21da86a6cd9d8d188f74117 100644
--- a/chrome/browser/resources/md_history/grouped_list.js
+++ b/chrome/browser/resources/md_history/grouped_list.js
@@ -35,9 +35,7 @@ Polymer({
     // An array of history entries in reverse chronological order.
     historyData: Array,
 
-    queryStartTime: String,
-
-    queryEndTime: String,
+    queryInterval: String,
 
     range: Number,
   },
@@ -125,7 +123,7 @@ Polymer({
     } else if (this.range == HistoryRange.MONTH) {
       // Group each all visits into a single list.
       this.groupedHistoryData_ = [{
-        title: this.queryStartTime + ' – ' + this.queryEndTime,
+        title: this.queryInterval,
         domains: this.createHistoryDomains_(this.historyData)
       }];
     }