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

chrome/common/render_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include <stdint.h>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
@@ skipping 306 matching lines @@
 // NetErrorHelper will receive this mesage and replace or update the error
 // page with more specific troubleshooting suggestions.
 IPC_MESSAGE_ROUTED1(ChromeViewMsg_NetErrorInfo,
                     int /* DNS probe status */)
 
 // Tells the renderer whether or not there is a local diagnostics service that
 // can be run via ChromeViewHostMsg_RunNetworkDiagnostics messages.
 IPC_MESSAGE_ROUTED1(ChromeViewMsg_SetCanShowNetworkDiagnosticsDialog,
                     bool /* can_show_network_diagnostics_dialog */)
 
+// Tells the renderer whether or not an offline page exists. This is used to
+// decide if "show saved pages" button will be provided on certain error page.
+IPC_MESSAGE_ROUTED1(ChromeViewMsg_SetHasOfflinePages,
+                    bool /* has_offline_pages */)
+
 // Provides the information needed by the renderer process to contact a
 // navigation correction service.  Handled by the NetErrorHelper.
 IPC_MESSAGE_ROUTED5(ChromeViewMsg_SetNavigationCorrectionInfo,
                     GURL /* Navigation correction service base URL */,
                     std::string /* language */,
                     std::string /* origin_country */,
                     std::string /* API key to use */,
                     GURL /* Google Search URL to use */)
 
 IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_RunNetworkDiagnostics,
                     GURL /* failed_url */)
 
+// Message sent from the renderer to the browser to show the UI for offline
+// pages.
+IPC_MESSAGE_ROUTED0(ChromeViewHostMsg_ShowOfflinePages)
+
 //-----------------------------------------------------------------------------
 // Misc messages
 // These are messages sent from the renderer to the browser process.
 
 IPC_MESSAGE_CONTROL1(ChromeViewHostMsg_UpdatedCacheStats,
                      blink::WebCache::UsageStats /* stats */)
 
 // Sent by the renderer process to check whether access to FileSystem is
 // granted by content settings.
 IPC_SYNC_MESSAGE_CONTROL3_1(ChromeViewHostMsg_RequestFileSystemAccessSync,
@@ skipping 224 matching lines @@
 
 // Record a sample string to a Rappor metric.
 IPC_MESSAGE_CONTROL2(ChromeViewHostMsg_RecordRappor,
                      std::string /* metric */,
                      std::string /* sample */)
 
 // Record a domain and registry of a url to a Rappor metric.
 IPC_MESSAGE_CONTROL2(ChromeViewHostMsg_RecordRapporURL,
                      std::string /* metric */,
                      GURL /* sample url */)