Add new flag for experimental app banners.

chrome/browser/flag_descriptions.cc

Index: chrome/browser/flag_descriptions.cc
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 97e977e48c52f4afa0617d754e03a348292c257a..183f225d462502060f4facf17cb41ce7f3203f01 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -359,6 +359,11 @@ const char kColorCorrectRenderingName[] = "Color correct rendering";
 const char kColorCorrectRenderingDescription[] =
     "Enables color correct rendering of web content.";
 
+const char kExperimentalAppBannersName[] = "Experimental app banners";
+
+const char kExperimentalAppBannersDescription[] =
+    "Enables a new experimental app banner flow and UI";
+
 const char kExperimentalCanvasFeaturesName[] = "Experimental canvas features";
 
 const char kExperimentalCanvasFeaturesDescription[] =