Don't allow elevation for CHROME_OS.

chrome/browser/resources/managed_mode_block_interstitial.js

Index: chrome/browser/resources/managed_mode_block_interstitial.js
diff --git a/chrome/browser/resources/managed_mode_block_interstitial.js b/chrome/browser/resources/managed_mode_block_interstitial.js
index 814d19a370a95c47871ea9ca26c375f4f130699e..cc4ce173bdb20e25acafad726927efdf58c27dd5 100644
--- a/chrome/browser/resources/managed_mode_block_interstitial.js
+++ b/chrome/browser/resources/managed_mode_block_interstitial.js
@@ -8,8 +8,10 @@ function sendCommand(cmd) {
 }
 
 function initialize() {
-  $('bypass-block-button').onclick = function(event) {
-    sendCommand('preview');
+  if (!cr.isChromeOS) {
+    $('bypass-block-button').onclick = function(event) {
+      sendCommand('preview');
+    }
   }
   $('back-button').onclick = function(event) {
     sendCommand('back');