Restore contextual_search javascript unit tests.

Bug: none
Change-Id: I658af99ffa8bb7ff7551da3c691f8d9e7e11c802
Reviewed-on: https://chromium-review.googlesource.com/724162Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509746}

ios/chrome/test/BUILD.gn

@@ -179,6 +179,7 @@ test("ios_chrome_unittests") {
     "//ios/chrome/browser/ui/content_suggestions/cells:unit_tests",
     "//ios/chrome/browser/ui/content_suggestions/identifier:unit_tests",
     "//ios/chrome/browser/ui/context_menu:unit_tests",
+    "//ios/chrome/browser/ui/contextual_search:unit_tests",
     "//ios/chrome/browser/ui/coordinators:unit_tests",
     "//ios/chrome/browser/ui/dialogs:unit_tests",
     "//ios/chrome/browser/ui/dialogs:unit_tests_internal",