MD History: Add lazy-render element for simple lazy initialization.

chrome/browser/resources/md_history/synced_device_manager.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/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_shared_menu/cr_shared_menu.html">
+<link rel="import" href="chrome://history/lazy_render.html">
 <link rel="import" href="chrome://history/shared_style.html">
 <link rel="import" href="chrome://history/synced_device_card.html">
 
 <dom-module id="history-synced-device-manager">
   <template>
     <style include="shared-style">
       :host {
         display: block;
         overflow: overlay;
       }
@@ skipping 63 matching lines @@
     <div id="sign-in-guide"
         hidden="[[!showSignInGuide(signInState_, guestSession_)]]">
       <div id="illustration"></div>
       <div id="sign-in-promo">$i18n{signInPromo}</div>
       <div id="sign-in-promo-desc">$i18n{signInPromoDesc}</div>
       <paper-button id="sign-in-button" on-tap="onSignInTap_">
         $i18n{signInButton}
       </paper-button>
     </div>
 
-    <cr-shared-menu id="menu">
-      <paper-item class="menu-item" on-tap="onOpenAllTap_">
-        $i18n{openAll}
-      </paper-item>
-      <paper-item class="menu-item" on-tap="onDeleteSessionTap_">
-        $i18n{deleteSession}
-      </paper-item>
-    </cr-shared-menu>
+    <template is="history-lazy-render" id="menu">
+      <cr-shared-menu>
+        <paper-item class="menu-item" on-tap="onOpenAllTap_">
+          $i18n{openAll}
+        </paper-item>
+        <paper-item class="menu-item" on-tap="onDeleteSessionTap_">
+          $i18n{deleteSession}
+        </paper-item>
+      </cr-shared-menu>
+    </template>
   </template>
   <script src="chrome://history/synced_device_manager.js"></script>
 </dom-module>