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

chrome/common/localized_error.h

 // Copyright (c) 2011 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 CHROME_COMMON_LOCALIZED_ERROR_H_
 #define CHROME_COMMON_LOCALIZED_ERROR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
 #include "url/gurl.h"
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace blink {
 struct WebURLError;
 }
 
 namespace error_page {
 struct ErrorPageParams;
 }
 
+enum class OfflinePageStatus {
+  // No offline page exists.
+  NONE,
+  // The offline copy of this page exists.
+  HAS_PAGE_COPY,
+  // The offline copy of this page does not exist, but the offline copies of
+  // other pages exist.
+  HAS_OTHER_COPIES,
+};
+
 class LocalizedError {
  public:
+
   // Fills |error_strings| with values to be used to build an error page used
   // on HTTP errors, like 404 or connection reset.
   static void GetStrings(int error_code,
                          const std::string& error_domain,
                          const GURL& failed_url,
                          bool is_post,
                          bool stale_copy_in_cache,
                          bool can_show_network_diagnostics_dialog,
-                         bool has_offline_pages,
+                         OfflinePageStatus offline_page_status,
                          const std::string& locale,
                          const std::string& accept_languages,
                          scoped_ptr<error_page::ErrorPageParams> params,
                          base::DictionaryValue* strings);
 
   // Returns a description of the encountered error.
   static base::string16 GetErrorDetails(const blink::WebURLError& error,
                                         bool is_post);
 
   // Returns true if an error page exists for the specified parameters.
   static bool HasStrings(const std::string& error_domain, int error_code);
 
   static const char kHttpErrorDomain[];
 
  private:
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(LocalizedError);
 };
 
 #endif  // CHROME_COMMON_LOCALIZED_ERROR_H_