Add a feature flag for enabling transparent doodle request.

chrome/browser/android/chrome_feature_list.cc

Index: chrome/browser/android/chrome_feature_list.cc
diff --git a/chrome/browser/android/chrome_feature_list.cc b/chrome/browser/android/chrome_feature_list.cc
index 2a32902632627b3a4b5758bcee03bf54db1620aa..1408e33f0ca769b84c01ffe19ffe0a9daf084f39 100644
--- a/chrome/browser/android/chrome_feature_list.cc
+++ b/chrome/browser/android/chrome_feature_list.cc
@@ -64,6 +64,10 @@ const base::Feature kNTPToolbarFeature {
   "NTPToolbar", base::FEATURE_ENABLED_BY_DEFAULT
 };
 
+const base::Feature kNTPTransparentDoodle {
+  "NTPTransparentDoodle", base::FEATURE_DISABLED_BY_DEFAULT
+};
+
 const base::Feature kNTPFakeOmniboxTextFeature {
   "NTPFakeOmniboxText", base::FEATURE_DISABLED_BY_DEFAULT
 };