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

ios/chrome/browser/reading_list/reading_list_model_impl.cc

Index: ios/chrome/browser/reading_list/reading_list_model_impl.cc
diff --git a/ios/chrome/browser/reading_list/reading_list_model_impl.cc b/ios/chrome/browser/reading_list/reading_list_model_impl.cc
index c3e068d65f0249a30a6ce1c36dbd381cdf56d260..a9d29cc59c014fb4b71034ed81194b2506d81abc 100644
--- a/ios/chrome/browser/reading_list/reading_list_model_impl.cc
+++ b/ios/chrome/browser/reading_list/reading_list_model_impl.cc
@@ -54,17 +54,35 @@ void ReadingListModelImpl::ResetUnseenEntries() {
     storageLayer_->SavePersistentHasUnseen(false);
 }
 
-// Returns a specific entry.
-const ReadingListEntry& ReadingListModelImpl::GetUnreadEntryAtIndex(
+const ReadingListEntry* ReadingListModelImpl::GetUnreadEntryAtIndex(
     size_t index) const {
   DCHECK(loaded());
-  return unread_[index];
+  if (index >= unread_.size())
+    return nullptr;
+  return &unread_[index];
 }
 
-const ReadingListEntry& ReadingListModelImpl::GetReadEntryAtIndex(
+const ReadingListEntry* ReadingListModelImpl::GetReadEntryAtIndex(
     size_t index) const {
   DCHECK(loaded());
-  return read_[index];
+  if (index >= read_.size())
+    return nullptr;
+  return &read_[index];
+}
+
+const ReadingListEntry* ReadingListModelImpl::GetEntryFromURL(
+    const GURL& gurl) const {
+  auto it = std::find_if(
+      read_.begin(), read_.end(),
+      [&gurl](const ReadingListEntry& entry) { return gurl == entry.URL(); });
+  if (it == read_.end()) {
+    it = std::find_if(
+        unread_.begin(), unread_.end(),
+        [&gurl](const ReadingListEntry& entry) { return gurl == entry.URL(); });
+    if (it == unread_.end())
+      return nullptr;
+  }
+  return &(*it);
 }
 
 bool ReadingListModelImpl::CallbackEntryURL(