MD History: Replace px-based font sizes with %-based sizing

chrome/browser/resources/md_history/side_bar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-selector/iron-selector.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-ripple/paper-ripple.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/typography.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-side-bar">
@@ skipping 44 matching lines @@
       iron-selector > a {
         @apply(--paper-font-subhead);
         /* Ensure the focus outline appears correctly (crbug.com/655503). */
         -webkit-margin-end: 4px;
         -webkit-padding-start: 24px;
         align-items: center;
         box-sizing: border-box;
         color: inherit;
         cursor: pointer;
         display: flex;
-        font-size: 14px;
+        font-size: 108%;
         font-weight: 500;
         min-height: 48px;
         position: relative;
         text-decoration: none;
       }
 
       iron-selector > a.iron-selected {
         color: var(--link-color);
       }
 
@@ skipping 40 matching lines @@
       </a>
       <div id="spacer"></div>
       <div id="footer" hidden="[[!showFooter]]">
         <div class="separator"></div>
         <div id="footer-text">$i18nRaw{sidebarFooter}</div>
       </div>
     </iron-selector>
   </template>
   <script src="chrome://history/side_bar.js"></script>
 </dom-module>