Add <a is="action-link">, a web component extension of <a> for in-page actions.

chrome/browser/resources/sync_setup_overlay.html

 <div id="sync-setup-overlay" class="page" hidden>
   <div class="close-button"></div>
   <div id="sync-setup-configure" hidden>
     <div id="confirm-sync-preferences">
       <h1 i18n-content="confirmSyncPreferences"></h1>
       <div id="sync-instructions-container" class="content-area">
         <span i18n-content="chooseDataTypesInstructions"></span>
         <a id="encryption-help-link" target="_blank"
             i18n-values="href:syncEverythingHelpURL" i18n-content="learnMore">
         </a>
       </div>
       <div>
         <div class="action-area">
           <div class="action-area-link-container">
-            <button id="customize-link" type="button"
-                i18n-content="customizeLinkLabel"
-                class="link-button">
-            </button>
+            <a is="action-link" id="customize-link"
+                i18n-content="customizeLinkLabel"></a>
           </div>
           <div id="confirm-everything-throbber" class="throbber"></div>
           <div class="button-strip">
             <input id="confirm-everything-cancel" type="button"
                 i18n-values="value:cancel">
             <input id="confirm-everything-ok" type="button"
                 i18n-values="value:syncEverything">
           </div>
         </div>
       </div>
@@ skipping 150 matching lines @@
                    i18n-content="incorrectPassphrase" hidden>
               </div>
             </div>
             <div id="sync-passphrase-warning"
                  i18n-values=".innerHTML:passphraseRecover" hidden>
             </div>
           </div>
         </div>
         <div class="action-area">
           <div class="action-area-link-container">
-            <button id="use-default-link" type="button"
-                i18n-content="useDefaultSettings"
-                class="link-button">
-            </button>
+            <a is="action-link" id="use-default-link"
+                i18n-content="useDefaultSettings"></a>
           </div>
           <div id="choose-datatypes-throbber" class="throbber"></div>
           <div class="button-strip">
             <input id="choose-datatypes-cancel" type="button"
                 i18n-values="value:cancel">
             <input id="choose-datatypes-ok" type="submit"
                 i18n-values="value:ok">
           </div>
         </div>
       </form>
@@ skipping 28 matching lines @@
 </if>
     </div>
     <div class="action-area button-strip">
       <input id="stop-syncing-cancel" type="button"
           i18n-values="value:cancel">
       <input id="stop-syncing-ok" type="button"
           i18n-values="value:stopSyncingConfirm">
     </div>
   </div>
 </div>