Showing previews UI for Offline Previews

components/offline_pages/request_header/offline_page_header.cc

Index: components/offline_pages/request_header/offline_page_header.cc
diff --git a/components/offline_pages/request_header/offline_page_header.cc b/components/offline_pages/request_header/offline_page_header.cc
index db7b7c9e56de125b4301f5628cd9bc67423ef4a5..3246954f149f8f9e730c47ed9899a79fb47691b1 100644
--- a/components/offline_pages/request_header/offline_page_header.cc
+++ b/components/offline_pages/request_header/offline_page_header.cc
@@ -78,20 +78,22 @@ std::string ReasonToString(OfflinePageHeader::Reason reason) {
 }
 
 }  // namespace
 
 OfflinePageHeader::OfflinePageHeader()
     : did_fail_parsing_for_test(false),
       need_to_persist(false),
       reason(Reason::NONE) {
 }
 
+OfflinePageHeader::OfflinePageHeader(const OfflinePageHeader& other) = default;
+
 OfflinePageHeader::OfflinePageHeader(const std::string& header_value)
     : did_fail_parsing_for_test(false),
       need_to_persist(false),
       reason(Reason::NONE) {
   if (!ParseOfflineHeaderValue(header_value, &need_to_persist, &reason, &id)) {
     did_fail_parsing_for_test = true;
     Clear();
   }
 }