PlzNavigate: Allow frames to fallback to alternative content.

third_party/WebKit/Source/core/html/HTMLObjectElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 37 matching lines @@
   DECLARE_VIRTUAL_TRACE();
 
   const String& classId() const { return m_classId; }
 
   HTMLFormElement* formOwner() const override;
 
   bool containsJavaApplet() const;
 
   bool hasFallbackContent() const override;
   bool useFallbackContent() const override;
+  bool canRenderFallbackContent() const override { return true; }
   void renderFallbackContent() override;
 
   bool isFormControlElement() const override { return false; }
 
   bool isEnumeratable() const override { return true; }
   bool isInteractiveContent() const override;
 
   // Implementations of constraint validation API.
   // Note that the object elements are always barred from constraint validation.
   String validationMessage() const override { return String(); }
@@ skipping 85 matching lines @@
       static_cast<const HTMLObjectElement&>(element);
   // We need to assert after the cast because FormAssociatedElement doesn't
   // have hasTagName.
   SECURITY_DCHECK(objectElement.hasTagName(HTMLNames::objectTag));
   return objectElement;
 }
 
 }  // namespace blink
 
 #endif  // HTMLObjectElement_h