Introduce Zero Prefix URL Suggestions flag.

This flag controls support for Omnibox Zero Prefix URL Suggestions on Clank.
When enabled, Omnibox will start supplying suggestions for currently visited
website.

Bug: 934922
Change-Id: Ic28e81855198c5a21e1c0e2eeee02629f422ca1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516713
Reviewed-by: Filip Gorski <[email protected]>
Reviewed-by: Matthew Jones <[email protected]>
Reviewed-by: Mark Pearson <[email protected]>
Commit-Queue: Ender <[email protected]>
Cr-Commit-Position: refs/heads/master@{#641327}
diff --git a/components/omnibox/browser/zero_suggest_provider.cc b/components/omnibox/browser/zero_suggest_provider.cc
index df6e08e..624728d7 100644
--- a/components/omnibox/browser/zero_suggest_provider.cc
+++ b/components/omnibox/browser/zero_suggest_provider.cc
@@ -514,11 +514,10 @@
 
 bool ZeroSuggestProvider::AllowZeroSuggestSuggestions(
     const GURL& current_page_url) const {
-  // Don't show zero suggest on the NTP.
-  // TODO(hfung): Experiment with showing MostVisited zero suggest on NTP
-  // under the conditions described in crbug.com/305366.
-  if (IsNTPPage(current_page_classification_))
+  if (IsNTPPage(current_page_classification_) &&
+      !base::FeatureList::IsEnabled(omnibox::kZeroSuggestionsOnNTP)) {
     return false;
+  }
 
   // Don't run if in incognito mode.
   if (client()->IsOffTheRecord())