[MD History] Disable clicks in the date header of cards.

chrome/browser/resources/md_history/history_item.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.
 
 /**
  * @param {!Element} root
  * @param {?Element} boundary
  * @param {cr.ui.FocusRow.Delegate} delegate
  * @constructor
  * @extends {cr.ui.FocusRow}
@@ skipping 175 matching lines @@
      * @param {MouseEvent} e
      * @private
      */
     onCheckboxMousedown_: function(e) {
       // Prevent shift clicking a checkbox from selecting text.
       if (e.shiftKey)
         e.preventDefault();
     },
 
     /**
+     * @param {MouseEvent} e
+     * @private
+     */
+    onTitleMousedown_: function(e) {
+      e.preventDefault();
+    },
+
+    /**
      * @private
      * @return {string}
      */
     getEntrySummary_: function() {
       var item = this.item;
       return loadTimeData.getStringF(
           'entrySummary', item.dateTimeOfDay,
           item.starred ? loadTimeData.getString('bookmarked') : '', item.title,
           item.domain);
     },
@@ skipping 116 matching lines @@
 
     if (searchedTerm)
       return currentItem.dateShort != nextItem.dateShort;
 
     return currentItem.time - nextItem.time > BROWSING_GAP_TIME &&
         currentItem.dateRelativeDay == nextItem.dateRelativeDay;
   };
 
   return { HistoryItem: HistoryItem };
 });