MD History: Fix minor visual inconsistencies

chrome/browser/resources/md_history/history_list.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-scroll-threshold/iron-scroll-threshold.html">
 <link rel="import" href="chrome://history/constants.html">
 <link rel="import" href="chrome://history/history_item.html">
 <link rel="import" href="chrome://history/history_list_behavior.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-list">
   <template>
     <style include="shared-style">
       :host {
         box-sizing: border-box;
         display: block;
         overflow: auto;
-        padding-top: var(--first-card-padding-top);
       }
 
       iron-list {
         @apply(--card-sizing);
+        margin-top: var(--first-card-padding-top);
       }
     </style>
     <div id="no-results" class="centered-message"
         hidden$="[[hasResults(historyData_.length)]]">
       {{noResultsMessage(searchedTerm, querying)}}
     </div>
     <iron-list items="{{historyData_}}" as="item" id="infinite-list"
         hidden$="[[!hasResults(historyData_.length)]]">
       <template>
         <history-item tabindex$="[[tabIndex]]"
@@ skipping 10 matching lines @@
             last-focused="{{lastFocused_}}">
         </history-item>
       </template>
     </iron-list>
     <iron-scroll-threshold id="scroll-threshold" scroll-target="infinite-list"
         lower-threshold="500" on-lower-threshold="loadMoreData_">
     </iron-scroll-threshold>
   </template>
   <script src="chrome://history/history_list.js"></script>
 </dom-module>