Refactors offline page tab helper to stash the offline page item on redirect.

chrome/browser/android/offline_pages/offline_page_utils.h

Index: chrome/browser/android/offline_pages/offline_page_utils.h
diff --git a/chrome/browser/android/offline_pages/offline_page_utils.h b/chrome/browser/android/offline_pages/offline_page_utils.h
index 6bccdc3d44497184a91878e4dda242b3f71029bd..ce694542497552ec8bce10f67db95c9308a1db5d 100644
--- a/chrome/browser/android/offline_pages/offline_page_utils.h
+++ b/chrome/browser/android/offline_pages/offline_page_utils.h
@@ -13,6 +13,7 @@ class GURL;
 
 namespace content {
 class BrowserContext;
+class WebContents;
 }
 
 namespace offline_pages {
@@ -58,6 +59,17 @@ class OfflinePageUtils {
   // Marks that the offline page related to the |offline_url| has been accessed.
   static void MarkPageAccessed(content::BrowserContext* browser_context,
                                const GURL& offline_url);
+
+  // Gets the offline page corresponding to the given web contents.  The
+  // returned pointer is owned by the web_contents and may be deleted by user
+  // navigation, so it is unsafe to store a copy of the returned pointer.
+  static const OfflinePageItem* GetCurrentOfflinePage(
+      content::WebContents* web_contents);
+
+  // Sets the offline page corresponding to the given web contents.  If
+  // |offline_page| contains |nullptr|, removes the page from the web contents.
+  static void SetCurrentOfflinePage(content::WebContents* web_contents,
+                                    const OfflinePageItem* offline_page);
 };
 
 }  // namespace offline_pages