Omnibox: Experiment with showing a generic icon for search suggestions

Instead of showing the Search Provider favicon in the omnibox, this
experiment shows a generic magnifying glass icon.

This also applies to the NTP, as the omnibox in the NTP has always had
the same icon as the omnibox showing a search suggestion.

Doing something different would require a more extensive change.

Bug: 931836
Change-Id: Ia16422b8e4c710b6d664d10c20a322b1083dd57a
Reviewed-on: https://chromium-review.googlesource.com/c/1471247Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632009}

chrome/browser/ui/omnibox/chrome_omnibox_client.cc

@@ -58,6 +58,7 @@
 #include "components/omnibox/browser/autocomplete_result.h"
 #include "components/omnibox/browser/location_bar_model.h"
 #include "components/omnibox/browser/omnibox_controller_emitter.h"
+#include "components/omnibox/browser/omnibox_field_trial.h"
 #include "components/omnibox/browser/search_provider.h"
 #include "components/prefs/pref_service.h"
 #include "components/search/search.h"
@@ -397,6 +398,13 @@ gfx::Image ChromeOmniboxClient::GetFaviconForPageUrl(
 
 gfx::Image ChromeOmniboxClient::GetFaviconForDefaultSearchProvider(
     FaviconFetchedCallback on_favicon_fetched) {
+  if (base::FeatureList::IsEnabled(
+          omnibox::kUIExperimentUseGenericSearchEngineIcon)) {
+    // Returning an empty image and never calling |on_favicon_fetched| will
+    // keep the generic icon showing for the default search provider.
+    return gfx::Image();
+  }
+
   const TemplateURL* const default_provider =
       GetTemplateURLService()->GetDefaultSearchProvider();
   if (!default_provider)

components/omnibox/browser/omnibox_field_trial.cc

@@ -245,6 +245,12 @@ const base::Feature kUIExperimentShowSuffixOnAllSearchSuggestions{
     "OmniboxUIExperimentShowSuffixOnAllSearchSuggestions",
     base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Feature used to show a generic vector icon for omnibox search instead of the
+// search engine favicon.
+extern const base::Feature kUIExperimentUseGenericSearchEngineIcon{
+    "OminboxUIExperimentUseGenericSearchEngineIcon",
+    base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Feature used to enable speculatively starting a service worker associated
 // with the destination of the default match when the user's input looks like a
 // query.

components/omnibox/browser/omnibox_field_trial.h

@@ -52,6 +52,7 @@ extern const base::Feature kUIExperimentShowSuggestionFavicons;
 extern const base::Feature kUIExperimentSwapTitleAndUrl;
 extern const base::Feature kUIExperimentVerticalMargin;
 extern const base::Feature kUIExperimentShowSuffixOnAllSearchSuggestions;
+extern const base::Feature kUIExperimentUseGenericSearchEngineIcon;
 extern const base::Feature kSpeculativeServiceWorkerStartOnQueryInput;
 extern const base::Feature kDocumentProvider;
 extern const base::Feature kOmniboxPopupShortcutIconsInZeroState;