App Banner: require 'display' to be set to 'standalone' or 'fullscreen'.

chrome/browser/banners/app_banner_debug_log.cc

Index: chrome/browser/banners/app_banner_debug_log.cc
diff --git a/chrome/browser/banners/app_banner_debug_log.cc b/chrome/browser/banners/app_banner_debug_log.cc
index 36f9c5da2c7e1bba5f72629395514cad9ef65468..40e93e654d010f9ae7f1cc7344917b6e8dc263ea 100644
--- a/chrome/browser/banners/app_banner_debug_log.cc
+++ b/chrome/browser/banners/app_banner_debug_log.cc
@@ -26,6 +26,8 @@ const char kUserNavigatedBeforeBannerShown[] =
 const char kStartURLNotValid[] = "start URL in manifest is not valid";
 const char kManifestMissingNameOrShortName[] =
     "one of manifest name or short name must be specified";
+const char kManifestDisplayStandaloneFullscreen[] =
+    "manifest display property must be set to 'standalone' or 'fullscreen'";
 const char kManifestMissingSuitableIcon[] =
     "manifest does not contain a suitable icon - PNG format of at least "
     "144x144px is required, and the sizes attribute must be set";