Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

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

Index: third_party/WebKit/Source/core/html/HTMLIFrameElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLIFrameElement.h b/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
index effd2136ba3a15f0eaa85457167b4413ffd16f37..df400a5ce3a3b77b5d781df3c982f4fe222fc722 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
@@ -57,6 +57,8 @@ class CORE_EXPORT HTMLIFrameElement final
  private:
   explicit HTMLIFrameElement(Document&);
 
+  void setShouldCollapse(bool) override;
+
   void parseAttribute(const AttributeModificationParams&) override;
   bool isPresentationAttribute(const QualifiedName&) const override;
   void collectStyleForPresentationAttribute(const QualifiedName&,
@@ -93,6 +95,7 @@ class CORE_EXPORT HTMLIFrameElement final
   bool m_didLoadNonEmptyDocument;
   bool m_allowFullscreen;
   bool m_allowPaymentRequest;
+  bool m_shouldCollapse;
   Member<HTMLIFrameElementSandbox> m_sandbox;
   Member<HTMLIFrameElementPermissions> m_permissions;
   Member<HTMLIFrameElementAllow> m_allow;