[iOS] Fix iOS dino

The previous version of the iOS detection of the dino wasn't using the
correct way of getting the user agent.

Bug: 1008774
Change-Id: I96d92a9f5da837509961cb4238e03c4b0d510a8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836497
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703034}

components/neterror/resources/offline.js

@@ -98,8 +98,8 @@ var IS_HIDPI = window.devicePixelRatio > 1;
 // but navigator.userAgent includes /Safari/.
 // TODO(crbug.com/998999): Fix navigator.userAgent such that it reliably
 // returns an agent string containing "CriOS".
-var IS_IOS = /iPad|iPhone|iPod|MacIntel/.test(navigator.platform) &&
-    !(/Safari/.test(navigator.userAgent));
+var IS_IOS = /iPad|iPhone|iPod|MacIntel/.test(window.navigator.platform) &&
+    !(/Safari/.test(window.navigator.userAgent));
 
 
 /** @const */