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

chrome/common/localized_error.h

Index: chrome/common/localized_error.h
diff --git a/chrome/common/localized_error.h b/chrome/common/localized_error.h
index 32374818b82ba0f713bf909b4420830919f0f110..8c3f5c7df29d05b12f082e709c0fa98f65eed978 100644
--- a/chrome/common/localized_error.h
+++ b/chrome/common/localized_error.h
@@ -24,8 +24,19 @@ 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,
@@ -34,7 +45,7 @@ class LocalizedError {
                          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,