Add "SHOW ALL SAVED PAGES" button to offline error page

components/error_page/common/net_error_info.h

Index: components/error_page/common/net_error_info.h
diff --git a/components/error_page/common/net_error_info.h b/components/error_page/common/net_error_info.h
index 77d6a283b2adb70e959104e3adb6ba5b3b39ce16..32d8dbabf7dfdf51ac41aea26b261d86c2270c80 100644
--- a/components/error_page/common/net_error_info.h
+++ b/components/error_page/common/net_error_info.h
@@ -41,6 +41,12 @@ enum NetworkErrorPageEvent {
 
   NETWORK_ERROR_DIAGNOSE_BUTTON_CLICKED = 17,      // Diagnose button clicked.
 
+  // For the "Show all saved pages".
+  NETWORK_ERROR_PAGE_SHOW_SAVED_PAGES_BUTTON_SHOWN = 18,
+  NETWORK_ERROR_PAGE_SHOW_SAVED_PAGES_BUTTON_CLICKED = 19,
+  NETWORK_ERROR_PAGE_SHOW_SAVED_PAGES_BUTTON_ERROR = 20,
+  NETWORK_ERROR_PAGE_BOTH_BUTTONS_SHOWN_SAVED_PAGES_CLICKED = 21,
+
   NETWORK_ERROR_PAGE_EVENT_MAX,
 };