Backfill some UI tests.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 1c996cf886798fbdff095b58ba92508a570f34f3..2d9272ce62f6976c0b2b2d19cc77dd8bd0ceb47f 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -4678,6 +4678,7 @@ test("unit_tests") {
         "../browser/ui/views/toolbar/toolbar_action_view_unittest.cc",
         "../browser/ui/views/toolbar/toolbar_actions_bar_bubble_views_unittest.cc",
         "../browser/ui/views/translate/translate_bubble_view_unittest.cc",
+        "../browser/ui/views/validation_message_bubble_view_unittest.cc",
         "../browser/ui/views/webshare/webshare_target_picker_view_unittest.cc",
       ]
     }