MD History: Lazily load element files which are not needed for first paint

chrome/browser/resources/md_history/app.html

Index: chrome/browser/resources/md_history/app.html
diff --git a/chrome/browser/resources/md_history/app.html b/chrome/browser/resources/md_history/app.html
index 9cda13e9a9cf119321e30c8595a9a780b0bfc04d..841e5c04e82104a9e88b67e7c730512e31a9e777 100644
--- a/chrome/browser/resources/md_history/app.html
+++ b/chrome/browser/resources/md_history/app.html
@@ -1,7 +1,6 @@
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/cr/ui.html">
 <link rel="import" href="chrome://resources/html/cr/ui/command.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/app-layout/app-drawer/app-drawer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/app-route/app-location.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/app-route/app-route.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-media-query/iron-media-query.html">
@@ -9,11 +8,12 @@
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-scroll-target-behavior/iron-scroll-target-behavior.html">
 <link rel="import" href="chrome://history/history_toolbar.html">
 <link rel="import" href="chrome://history/list_container.html">
-<link rel="import" href="chrome://history/synced_device_manager.html">
 <link rel="import" href="chrome://history/side_bar.html">
 <link rel="import" href="chrome://history/shared_style.html">
 <link rel="stylesheet" href="chrome://resources/css/md_colors.css">
 
+<!-- Lazy loaded: history-synced-device-manager, app-drawer. -->
+
 <dom-module id="history-app">
   <template>
     <style no-process>
@@ -52,6 +52,10 @@
         height: 100%;
       }
 
+      #drawer:unresolved {
+        display: none;
+      }
+
       #drawer-header {
         align-items: center;
         border-bottom: 1px solid rgba(0, 0, 0, 0.08);