Add "Show saved copy" button in dino page when there's offline copy

components/error_page/common/net_error_info.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_ERROR_PAGE_COMMON_NET_ERROR_INFO_H_
 #define COMPONENTS_ERROR_PAGE_COMMON_NET_ERROR_INFO_H_
 
 namespace error_page {
 
 // Network error page events.  Used for UMA statistics.
@@ skipping 23 matching lines @@
 
   // For "Google cached copy" button experiment.
   NETWORK_ERROR_PAGE_CACHED_COPY_BUTTON_SHOWN = 13,
   NETWORK_ERROR_PAGE_CACHED_COPY_BUTTON_CLICKED = 14,
   // Obsolete. No longer experimenting with the label.
   // NETWORK_ERROR_PAGE_CACHED_PAGE_BUTTON_SHOWN = 15,
   // NETWORK_ERROR_PAGE_CACHED_PAGE_BUTTON_CLICKED = 16,
 
   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,
+  // For the button to show all offline pages.
+  NETWORK_ERROR_PAGE_SHOW_OFFLINE_PAGES_BUTTON_SHOWN = 18,
+  NETWORK_ERROR_PAGE_SHOW_OFFLINE_PAGES_BUTTON_CLICKED = 19,
+
+  // For the button to show offline copy.
+  NETWORK_ERROR_PAGE_SHOW_OFFLINE_COPY_BUTTON_SHOWN = 20,
+  NETWORK_ERROR_PAGE_SHOW_OFFLINE_COPY_BUTTON_CLICKED = 21,
 
   NETWORK_ERROR_PAGE_EVENT_MAX,
 };
 
 // The status of a DNS probe.
 //
 // The DNS_PROBE_FINISHED_* values are used in histograms, so:
 // 1. FINISHED_UNKNOWN must remain the first FINISHED_* value.
 // 2. FINISHED_* values must not be rearranged relative to FINISHED_UNKNOWN.
 // 3. New FINISHED_* values must be inserted at the end.
@@ skipping 46 matching lines @@
 // Record specific error page events.
 void RecordEvent(NetworkErrorPageEvent event);
 
 // The error domain used to pass DNS probe statuses to the localized error
 // code.
 extern const char kDnsProbeErrorDomain[];
 
 }  // namespace error_page
 
 #endif  // COMPONENTS_ERROR_PAGE_COMMON_NET_ERROR_INFO_H_