Add grey triangle experiment flag on iOS

Matches the about_flags.cc implementation.

Bug: 1008219
Change-Id: I3755cf4f7b968fc347acc0ae5ab6ef31c70223bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884755Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Livvie Lin <livvielin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710126}

ios/chrome/browser/flags/about_flags.mm

@@ -93,13 +93,18 @@ const FeatureEntry::FeatureParam kMarkHttpAsWarningAndDangerousOnFormEdits[] = {
     {security_state::features::kMarkHttpAsFeatureParameterName,
      security_state::features::
          kMarkHttpAsParameterWarningAndDangerousOnFormEdits}};
+const FeatureEntry::FeatureParam kMarkHttpAsDangerWarning[] = {
+    {security_state::features::kMarkHttpAsFeatureParameterName,
+     security_state::features::kMarkHttpAsParameterDangerWarning}};
 
 const FeatureEntry::FeatureVariation kMarkHttpAsFeatureVariations[] = {
     {"(mark as actively dangerous)", kMarkHttpAsDangerous,
      base::size(kMarkHttpAsDangerous), nullptr},
     {"(mark with a Not Secure warning and dangerous on form edits)",
      kMarkHttpAsWarningAndDangerousOnFormEdits,
-     base::size(kMarkHttpAsWarningAndDangerousOnFormEdits), nullptr}};
+     base::size(kMarkHttpAsWarningAndDangerousOnFormEdits), nullptr},
+    {"(mark with a grey triangle icon)", kMarkHttpAsDangerWarning,
+     base::size(kMarkHttpAsDangerWarning), nullptr}};
 
 const FeatureEntry::Choice kUseDdljsonApiChoices[] = {
     {flags_ui::kGenericExperimentChoiceDefault, "", ""},