Omnibox UI Refresh: Implement textfield jogging behind a flag

This implements the previously-removed textfield jogging behavior
behind a feature flag accessible from chrome://flags.

Followup work: We may implement a special accommodation to the jog flag
to make the keystroke-backspace case less jarring of a transition.

Bug: 868157
Change-Id: I63fbb8f8f171f1d5ccf09f1cd92332963f567ae3
Reviewed-on: https://chromium-review.googlesource.com/1152459
Commit-Queue: Tommy Li <[email protected]>
Reviewed-by: Justin Donnelly <[email protected]>
Cr-Commit-Position: refs/heads/master@{#578666}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index a1e6992f..1f78d6c 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3240,6 +3240,11 @@
      FEATURE_VALUE_TYPE(
          omnibox::kUIExperimentHideSteadyStateUrlSchemeAndSubdomains)},
 
+    {"omnibox-ui-jog-textfield-on-popup",
+     flag_descriptions::kOmniboxUIJogTextfieldOnPopupName,
+     flag_descriptions::kOmniboxUIJogTextfieldOnPopupDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(omnibox::kUIExperimentJogTextfieldOnPopup)},
+
     {"omnibox-ui-show-suggestion-favicons",
      flag_descriptions::kOmniboxUIShowSuggestionFaviconsName,
      flag_descriptions::kOmniboxUIShowSuggestionFaviconsDescription, kOsDesktop,