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 c49204af92dc9c9ec43e1902ab33e52a71de885c..f15a2c798b7ad1e286d4bc3eac7623d85661cf72 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.h
@@ -53,6 +53,8 @@ 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&,
@@ -89,6 +91,7 @@ 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;