Nux Onboarding: make focus ring more obvious

Bug: 914180
Change-Id: I4a6fe2c4b984ea6f1aad596a53102b66d08c73d0
Reviewed-on: https://chromium-review.googlesource.com/c/1373014Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616104}

chrome/browser/resources/welcome/onboarding_welcome/shared/chooser_shared_css.html

@@ -36,7 +36,7 @@
       }
 
       .option.keyboard-focused:focus {
-        outline: -webkit-focus-ring-color auto 5px;
+        outline: rgba(26, 115, 232, 0.4) solid 3px;
       }
 
       .option .option-name {