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

chrome/browser/resources/md_history/history_item.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/cr/ui/focus_row.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="chrome://resources/html/icon.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/constants.html">
 <link rel="import" href="chrome://history/searched_label.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <!-- Lazy loaded: paper-icon-button-light. -->
 
 <dom-module id="history-item">
   <template>
     <style include="shared-style">
       :host {
         --checked-color: rgb(68, 136, 255);
         display: block;
         outline: none;
+        pointer-events: none;
       }
 
       /** Unresolved paper-icon-button-light styles. */
       button {
         background: none;
         border: none;
         outline: none;
         padding: 0;
       }
 
@@ skipping 14 matching lines @@
       }
 
       :host([is-card-start]) #date-accessed {
         display: block;
       }
 
       #item-container {
         align-items: center;
         display: flex;
         min-height: var(--item-height);
+        pointer-events: auto;
       }
 
       :host([is-card-start]) #item-container {
         padding-top: var(--card-first-last-item-padding);
       }
 
       :host([is-card-end]) #item-container {
         padding-bottom: var(--card-first-last-item-padding);
       }
 
@@ skipping 179 matching lines @@
           <div></div>
           <div></div>
           <div></div>
         </button>
       </div>
       <div id="time-gap-separator" hidden="[[!hasTimeGap]]"></div>
     </div>
   </template>
   <script src="chrome://history/history_item.js"></script>
 </dom-module>