Update WebUIFactory for ephemeral Guest profiles.

WebUIFactory is updated to deny bookmarks and new-tab-page for ephemeral
Guest profiles.

Please see go/ephemeral-guest-profiles for more context.

Bug: 1125474
Change-Id: I2ca675330402d656eb2afc5a691e4d59a2385f1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567395Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832694}

chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc

@@ -610,6 +610,11 @@ WebUIFactoryFunction GetWebUIFactoryFunction(WebUI* web_ui,
        url.host_piece() == chrome::kChromeUINewTabPageHost)) {
     return &NewWebUI<PageNotAvailableForGuestUI>;
   }
+  if (profile->IsEphemeralGuestProfile() &&
+      (url.host_piece() == chrome::kChromeUIBookmarksHost ||
+       url.host_piece() == chrome::kChromeUINewTabPageHost)) {
+    return &NewWebUI<PageNotAvailableForGuestUI>;
+  }
   // Bookmarks are part of NTP on Android.
   if (url.host_piece() == chrome::kChromeUIBookmarksHost)
     return &NewWebUI<BookmarksUI>;