Add GetEntryFromURL method to the ReadingListModel.

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 052bbe1ce47a3f5fa18a30106c15f904d0306d60..625b19f5f2b503e458bb5f8b9603978f31ea8c02 100644
--- a/ios/chrome/browser/reading_list/reading_list_model.h
+++ b/ios/chrome/browser/reading_list/reading_list_model.h
@@ -53,10 +53,14 @@ class ReadingListModel {
   virtual bool HasUnseenEntries() const = 0;
   virtual void ResetUnseenEntries() = 0;
 
+  // TODO(659099): Remove methods.
   // 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 null if the entry does not exist.
+  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.
   // Returns whether the callback has been called.