[OsSettingsLanguages] Add flag to virtual keyboard extension

Adding flag to extension so we can direct users correctly when opening
edit dictionary page.

Bug: 1144084
Change-Id: I6b8993f5d5e466c57aa0cead209139c631f9c17b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2513305
Commit-Queue: My Nguyen <myy@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823362}

chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc

@@ -437,6 +437,10 @@ void ChromeVirtualKeyboardDelegate::OnHasInputDevices(
       GenerateFeatureFlag("systemlatinphysicaltyping",
                           base::FeatureList::IsEnabled(
                               chromeos::features::kSystemLatinPhysicalTyping)));
+  features->AppendString(
+      GenerateFeatureFlag("languagesettingsupdate",
+                          base::FeatureList::IsEnabled(
+                              chromeos::features::kLanguageSettingsUpdate)));
 
   results->Set("features", std::move(features));