Changing scroll and view state in onpopstate shouldn't overwrite back/forward state restore

third_party/WebKit/Source/core/loader/HistoryItem.h

 /*
  * Copyright (C) 2006, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Research In Motion Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 41 matching lines @@
   ~HistoryItem();
 
   const String& UrlString() const;
   KURL Url() const;
 
   const Referrer& GetReferrer() const;
 
   EncodedFormData* FormData();
   const AtomicString& FormContentType() const;
 
-  void SetDidSaveScrollOrScaleState(bool did_save_scroll_or_scale_state) {
-    did_save_scroll_or_scale_state_ = did_save_scroll_or_scale_state;
+  class ViewState {
+   public:
+    ViewState() : page_scale_factor_(0) {}
+    ViewState(const ViewState&) = default;
+
+    ScrollOffset visual_viewport_scroll_offset_;
+    ScrollOffset scroll_offset_;
+    float page_scale_factor_;
+  };
+
+  ViewState* GetViewState() const { return view_state_.get(); }
+  void ClearViewState() { view_state_.reset(); }
+  void CopyViewStateFrom(HistoryItem* other) {
+    if (other->view_state_)
+      view_state_ = WTF::MakeUnique<ViewState>(*other->view_state_.get());

[majidvp, 2017/07/17 20:06:15]

shouldn't we reset() in the nullptr case?

[Nate Chapin, 2017/07/17 20:38:43]

That is closer to the old behavior, yes. Done.

   }
 
-  bool DidSaveScrollOrScaleState() const {
-    return did_save_scroll_or_scale_state_;
-  }
-
-  const ScrollOffset& VisualViewportScrollOffset() const;
   void SetVisualViewportScrollOffset(const ScrollOffset&);
-  const ScrollOffset& GetScrollOffset() const;
   void SetScrollOffset(const ScrollOffset&);
-
-  float PageScaleFactor() const;
   void SetPageScaleFactor(float);
 
   Vector<String> GetReferencedFilePaths();
   const Vector<String>& GetDocumentState();
   void SetDocumentState(const Vector<String>&);
   void SetDocumentState(DocumentState*);
   void ClearDocumentState();
 
   void SetURL(const KURL&);
   void SetURLString(const String&);
@@ skipping 26 matching lines @@
   ResourceRequest GenerateResourceRequest(WebCachePolicy);
 
   DECLARE_TRACE();
 
  private:
   HistoryItem();
 
   String url_string_;
   Referrer referrer_;
 
-  bool did_save_scroll_or_scale_state_;
-  ScrollOffset visual_viewport_scroll_offset_;
-  ScrollOffset scroll_offset_;
-  float page_scale_factor_;
   Vector<String> document_state_vector_;
   Member<DocumentState> document_state_;
 
+  std::unique_ptr<ViewState> view_state_;
+
   // If two HistoryItems have the same item sequence number, then they are
   // clones of one another. Traversing history from one such HistoryItem to
   // another is a no-op. HistoryItem clones are created for parent and
   // sibling frames when only a subframe navigates.
   int64_t item_sequence_number_;
 
   // If two HistoryItems have the same document sequence number, then they
   // refer to the same instance of a document. Traversing history from one
   // such HistoryItem to another preserves the document.
   int64_t document_sequence_number_;
 
   // Type of the scroll restoration for the history item determines if scroll
   // position should be restored when it is loaded during history traversal.
   HistoryScrollRestorationType scroll_restoration_type_;
 
   // Support for HTML5 History
   RefPtr<SerializedScriptValue> state_object_;
 
   // info used to repost form data
   RefPtr<EncodedFormData> form_data_;
   AtomicString form_content_type_;
 };  // class HistoryItem
 
 }  // namespace blink
 
 #endif  // HISTORYITEM_H