[MD History] Fix toolbar dates in grouped mode.

chrome/browser/resources/md_history/history_toolbar.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 Polymer({
   is: 'history-toolbar',
   properties: {
     // Number of history items currently selected.
     // TODO(calamity): bind this to
     // listContainer.selectedItem.selectedPaths.length.
@@ skipping 33 matching lines @@
       type: Number,
       reflectToAttribute: true,
       notify: true,
     },
 
     groupedOffset: {
       type: Number,
       notify: true,
     },
 
+    hasMoreResults: Boolean,
+
     querying: Boolean,
 
-    hasMoreResults: Boolean,
-
-    // The start time of the query range.
-    queryStartTime: String,
-
-    // The end time of the query range.
-    queryEndTime: String,
+    queryInfo: Object,

[calamity, 2016/12/15 02:17:52]

Just FYI, I considered adding a couple more String properties here but if the
same values ever came back when the range changed, (e.g switching from Week to
Month on the 7th), then the computed value wouldn't get updated. So....
queryInfo it is.

 
     // Whether to show the menu promo (a tooltip that points at the menu button
     // in narrow mode).
     showMenuPromo: Boolean,
   },
 
   /** @return {CrToolbarSearchFieldElement} */
   get searchField() {
     return /** @type {CrToolbarElement} */ (this.$['main-toolbar'])
         .getSearchField();
@@ skipping 51 matching lines @@
   deletingAllowed_: function() {
     return loadTimeData.getBoolean('allowDeletingHistory');
   },
 
   /** @private */
   numberOfItemsSelected_: function(count) {
     return count > 0 ? loadTimeData.getStringF('itemsSelected', count) : '';
   },
 
   /** @private */
-  getHistoryInterval_: function(queryStartTime, queryEndTime) {
-    // TODO(calamity): Fix the format of these dates.
-    return loadTimeData.getStringF(
-      'historyInterval', queryStartTime, queryEndTime);
+  getHistoryInterval_: function() {
+    var info = this.queryInfo;
+    if (this.groupedRange == HistoryRange.WEEK) {
+      return loadTimeData.getStringF(
+        'historyInterval', info.queryStartTimeShort, info.queryEndTimeShort);
+    }
+
+    if (this.groupedRange == HistoryRange.MONTH)
+      return info.queryStartMonth;
   },
 
   /** @private */
   onTodayTap_: function() {
     if (!this.querying)
       this.groupedOffset = 0;
   },
 
   /** @private */
   onPrevTap_: function() {
     if (!this.querying)
       this.groupedOffset = this.groupedOffset + 1;
   },
 
   /** @private */
   onNextTap_: function() {
     if (!this.querying)
       this.groupedOffset = this.groupedOffset - 1;
   },
 
   /**
    * @private
    * @return {boolean}
    */
   isToday_: function() { return this.groupedOffset == 0; },
 });