Fixes for cr-settings-date-time-page

BUG=485381

Review URL: https://codereview.chromium.org/1135733005

Cr-Commit-Position: refs/heads/master@{#329560}

chrome/browser/resources/settings/date_time_page/date_time_page.html

 <link rel="import" href="chrome://md-settings/checkbox/checkbox.html">
-<link rel="import" href="chrome://resources/polymer/polymer/polymer.html">
+<link rel="import" href="chrome://resources/polymer/v0_8/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v0_8/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v0_8/paper-material/paper-material.html">
 

chrome/browser/resources/settings/date_time_page/date_time_page.js

@@ -44,15 +44,17 @@ Polymer({
      */
     subpage: {
       type: Boolean,
-      value: false
-    }
+      value: false,
+      readOnly: true
+    },
 
     /**
      * ID of the page.
      */
     PAGE_ID: {
       type: String,
-      value: 'date-time'
+      value: 'date-time',
+      readOnly: true
     },
 
     /**
@@ -68,7 +70,8 @@ Polymer({
      */
     icon: {
       type: String,
-      value: 'device:access-time'
+      value: 'device:access-time',
+      readOnly: true
     },
   },
 });