Add GetEntryFromURL method to the ReadingListModel.

ios/chrome/browser/reading_list/reading_list_model_impl.h

Index: ios/chrome/browser/reading_list/reading_list_model_impl.h
diff --git a/ios/chrome/browser/reading_list/reading_list_model_impl.h b/ios/chrome/browser/reading_list/reading_list_model_impl.h
index 3293724d9ddbe06bd880a0c52074509572b29a06..0ae3b3c48161bb6c4c36467e9c4186913c2b2035 100644
--- a/ios/chrome/browser/reading_list/reading_list_model_impl.h
+++ b/ios/chrome/browser/reading_list/reading_list_model_impl.h
@@ -25,8 +25,11 @@ class ReadingListModelImpl : public ReadingListModel, public KeyedService {
   ReadingListModelImpl();
 
   ~ReadingListModelImpl() override;
+
+  // KeyedService implementation.
   void Shutdown() override;
 
+  // ReadingListModel implementation.
   bool loaded() const override;
 
   size_t unread_size() const override;
@@ -35,10 +38,11 @@ class ReadingListModelImpl : public ReadingListModel, public KeyedService {
   bool HasUnseenEntries() const override;
   void ResetUnseenEntries() override;
 
-  // Returns a specific entry.
   const ReadingListEntry& GetUnreadEntryAtIndex(size_t index) const override;
   const ReadingListEntry& GetReadEntryAtIndex(size_t index) const override;
 
+  const ReadingListEntry* GetEntryFromURL(const GURL& gurl) const override;
+
   bool CallbackEntryURL(
       const GURL& url,
       base::Callback<void(const ReadingListEntry&)> callback) const override;