MD History: Remove isFirstItem property from history-item

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/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-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.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">
 
 <dom-module id="history-item">
   <template>
     <style include="shared-style">
       :host {
         --checked-color: rgb(68, 136, 255);
         display: block;
       }
 
       :host(:not([embedded])) #main-container {
         position: relative;
       }
 
       :host(:not([embedded])) #sizing-container {
         @apply(--card-sizing);
       }
 
-      :host([is-first-item]) #main-container {
-        margin-top: var(--first-card-padding-top);
-      }
-
       :host([is-card-end]) #main-container {
         margin-bottom: var(--card-padding-between);
       }
 
       :host([is-card-start][is-card-end]) #main-container {
         border-radius: 2px;
       }
 
       #date-accessed {
         display: none;
@@ skipping 201 matching lines @@
             <div></div>
             <div></div>
           </button>
         </div>
         <div id="time-gap-separator" hidden="[[!hasTimeGap]]"></div>
       </div>
     </div>
   </template>
   <script src="chrome://history/history_item.js"></script>
 </dom-module>