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

chrome/browser/resources/md_history/shared_style.html

 <link rel="import" href="chrome://history/shared_vars.html">
 
 <dom-module id="shared-style">
   <template>
     <style>
       [hidden] {
         display: none !important;
       }
 
       a {
         color: var(--link-color);
       }
 
       .card-title {
         align-items: center;
         border-bottom: 1px solid var(--card-border-color);
         border-radius: 2px 2px 0 0;
         display: flex;
-        font-size: 14px;
+        font-size: 108%;
         font-weight: 500;
         height: 48px;
         line-height: 48px;
         overflow: hidden;
         padding: 0 20px;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
 
       .centered-message {
         align-items: center;
         color: var(--md-loading-message-color);
         display: flex;
         flex: 1;
-        font-size: 14px;
+        font-size: 108%;
         font-weight: 500;
         height: 100%;
         justify-content: center;
       }
 
       .website-icon {
         -webkit-margin-end: 16px;
         background-repeat: no-repeat;
         background-size: 16px;
         height: 16px;
@@ skipping 30 matching lines @@
       button.more-vert-button div {
         border: 2px solid var(--secondary-text-color);
         border-radius: 2px;
         margin: 1px 8px;
         pointer-events: none;
         transform: scale(0.8);
       }
     </style>
   </template>
 </dom-module>