Add new flag for experimental app banners.

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index b01c7f8a23c087b246edef09435adcdfeb75a83e..25534a5ca7f5c820bac37db411a312921e9d4fcf 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -152,6 +152,11 @@ const base::Feature kDisplayPersistenceToggleInPermissionPrompts{
 const base::Feature kExpectCTReporting{"ExpectCTReporting",
                                        base::FEATURE_ENABLED_BY_DEFAULT};
 
+// An experimental way of showing app banners, which has modal banners and gives
+// developers more control over when to show them.
+const base::Feature kExperimentalAppBanners{"ExperimentalAppBanners",
+                                            base::FEATURE_DISABLED_BY_DEFAULT};
+
 // An experimental fullscreen prototype that allows pages to map browser and
 // system-reserved keyboard shortcuts.
 const base::Feature kExperimentalKeyboardLockUI{