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

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 305 matching lines @@
 // 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 */)
 
 #if defined(OS_ANDROID)
-// 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 */)
+// Tells the renderer about the status of the offline pages. This is used to
+// decide if offline related button will be provided on certain error page.
+IPC_MESSAGE_ROUTED1(ChromeViewMsg_SetOfflinePageInfo,
+                    int /* offline_page_status */)
 #endif
 
 // 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 */)
 
 #if defined(OS_ANDROID)
 // Message sent from the renderer to the browser to show the UI for offline
 // pages.
 IPC_MESSAGE_ROUTED0(ChromeViewHostMsg_ShowOfflinePages)
+
+// Message sent from the renderer to the browser to load the offline copy of
+// the page that fails to load due to no internet.
+IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_LoadOfflineCopy,
+                    GURL /* url */)

[dcheng, 2015/11/13 19:40:25]

Since the renderer controls this parameter, doesn't this mean it can load the
offline copy for any page? Are there any security implications to this? From the
design, it looks like we plan on using MHTML right now (which can't run scripts
for security reasons).

[jianli, 2015/11/13 22:32:13]

Yes, the renderer could send the IPC to load the offline page, but only the
error page handler has the logic to do that, not any other pages.

Yes, we're using MHTML which does not support running scripts.

 #endif

[dcheng, 2015/11/13 19:40:25]

Can we add an // defined(OS_ANDROID) comment here?

[jianli, 2015/11/13 22:32:13]

Done.

 
 //-----------------------------------------------------------------------------
 // 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.
@@ skipping 220 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 */)