Load offline page if reading list entry takes more than 1s to load.

ios/chrome/browser/reading_list/reading_list_model.h

Index: ios/chrome/browser/reading_list/reading_list_model.h
diff --git a/ios/chrome/browser/reading_list/reading_list_model.h b/ios/chrome/browser/reading_list/reading_list_model.h
index 9dc2d38240121d75af757cbab94eedcd46297039..27acd77da2a0017a574b73863bfc9e4279e8cace 100644
--- a/ios/chrome/browser/reading_list/reading_list_model.h
+++ b/ios/chrome/browser/reading_list/reading_list_model.h
@@ -53,9 +53,10 @@ class ReadingListModel {
   virtual bool HasUnseenEntries() const = 0;
   virtual void ResetUnseenEntries() = 0;
 
-  // Returns a specific entry.
-  virtual const ReadingListEntry& GetUnreadEntryAtIndex(size_t index) const = 0;
-  virtual const ReadingListEntry& GetReadEntryAtIndex(size_t index) const = 0;
+  // Returns a specific entry. Returns nullptr if the entry does not exist.
+  virtual const ReadingListEntry* GetUnreadEntryAtIndex(size_t index) const = 0;
+  virtual const ReadingListEntry* GetReadEntryAtIndex(size_t index) const = 0;
+  virtual const ReadingListEntry* GetEntryFromURL(const GURL& gurl) const = 0;
 
   // Synchronously calls the |callback| with entry associated with this |url|.
   // Does nothing if there is no entry associated.