Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/flag_descriptions.h

Index: chrome/browser/flag_descriptions.h
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 9e97ec7c9d7d892dd9a82f229e86008569aca074..2be6ffb2a81b77f4f08b8835933b3aa8226f71e0 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -2216,6 +2216,14 @@ extern const char kOfflinePagesSvelteConcurrentLoadingName[];
 // (512MB RAM) devices.
 extern const char kOfflinePagesSvelteConcurrentLoadingDescription[];
 
+// Name for the flag to enable collecting load completeness signals to improve
+// prerendering snapshot timing.
+extern const char kOfflinePagesLoadSignalCollectingName[];
+
+// Description for the flag to enable collecting load timing signals to improve
+// prerendering snapshot timing.
+extern const char kOfflinePagesLoadSignalCollectingDescription[];
+
 // Name for the flag to enable offline pages to be prefetched.
 extern const char kOfflinePagesPrefetchingName[];