Load live version when reloading an offline page on connected network

components/offline_pages/request_header/offline_page_header.h

Index: components/offline_pages/request_header/offline_page_header.h
diff --git a/components/offline_pages/request_header/offline_page_header.h b/components/offline_pages/request_header/offline_page_header.h
new file mode 100644
index 0000000000000000000000000000000000000000..f7b0e562f744d9668392fc7b791d6c055fd3a86b
--- /dev/null
+++ b/components/offline_pages/request_header/offline_page_header.h
@@ -0,0 +1,79 @@
+// Copyright 2016 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 COMPONENTS_OFFLINE_PAGES_REQUEST_HEADER_OFFLINE_PAGE_HEADER_H_
+#define COMPONENTS_OFFLINE_PAGES_REQUEST_HEADER_OFFLINE_PAGE_HEADER_H_
+
+#include <string>
+
+namespace offline_pages {
+
+// Header that defines the custom behavior to load offline pages. Its value is a
+// comma/space separated name-value pair.
+extern const char kOfflinePageHeader[];
+
+// The name used in name-value pair of kOfflinePageHeader to tell if the offline
+// info in this header should be persisted across session restore.
+extern const char kOfflinePageHeaderPersistKey[];
+
+// The name used in name-value pair of kOfflinePageHeader to denote the reason
+// for loading offline page.
+extern const char kOfflinePageHeaderReasonKey[];
+// Possible values in name-value pair that denote the reason for loading offline
+// page.
+// The offline page should be loaded even when the network is connected. This is
+// because the live version failed to load due to certain net error.
+extern const char kOfflinePageHeaderReasonValueDueToNetError[];
+// The offline page should be loaded because the user clicks to open the
+// downloaded page explicitly.
+extern const char kOfflinePageHeaderReasonValueFromDownload[];
+// This only happens after the offline page is loaded due to above reason and
+// then the user reload current page. The network condition should be checked
+// this time to decide if a live version should be tried again.
+extern const char kOfflinePageHeaderReasonValueReload[];
+
+// The name used in name-value pair of kOfflinePageHeader to denote the offline
+// ID of the offline page to load.
+extern const char kOfflinePageHeaderIDKey[];
+
+// Used to parse the extra request header string that defines offline page
+// loading behaviors.
+struct OfflinePageHeader {
+ public:
+  enum class Reason {
+    NONE,
+    NET_ERROR,
+    DOWNLOAD,
+    RELOAD
+  };
+
+  OfflinePageHeader();
+
+  // Constructed from a request header value string.

[Dmitry Titov, 2016/09/17 02:22:54]

Please add comment here that if parse fails it's equivalent to calling Clear().

[jianli, 2016/09/19 21:29:05]

Done.

+  explicit OfflinePageHeader(const std::string& header_value);
+
+  ~OfflinePageHeader();
+
+  // Returns the full header string, including both key and value, that could be
+  // passed to set extra request header.
+  std::string GetCompleteHeaderString() const;
+
+  void Clear();
+
+  // Returns false if failed to construct from a request header value string.
+  bool is_valid;

[Dmitry Titov, 2016/09/17 02:22:54]

This is only useful for tests, to see if parsing failed. Can be named as
did_fail_parsing_for_test, for clarity.
Also, should not reset to false in Clear()... Once failed, should always be
true.

You Clear() on failed parse, which is perfect reaction to failure (invalid
header ignored), so this bool is not needed in the rest of the code.

[jianli, 2016/09/19 21:29:05]

Done.

+
+  // Flag to indicate if the header should be persisted across session restore.
+  bool need_to_persist;
+
+  // Describes the reason to load offline page.
+  Reason reason;
+
+  // The offline ID of the page to load.
+  std::string id;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_REQUEST_HEADER_OFFLINE_PAGE_HEADER_H_