Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

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

Index: third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp b/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
index 6f13781c84c15f403811150eaae2479a0c74c964..077963821b50075ca116e06f7283d3061d1c59ef 100644
--- a/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLIFrameElement.cpp
@@ -39,6 +39,7 @@ using namespace HTMLNames;
 inline HTMLIFrameElement::HTMLIFrameElement(Document& document)
     : HTMLFrameElementBase(iframeTag, document),
       m_didLoadNonEmptyDocument(false),
+      m_shouldCollapse(false),
       m_sandbox(HTMLIFrameElementSandbox::create(this)),
       m_referrerPolicy(ReferrerPolicyDefault) {}
 
@@ -53,6 +54,17 @@ DEFINE_TRACE(HTMLIFrameElement) {
 
 HTMLIFrameElement::~HTMLIFrameElement() {}
 
+void HTMLIFrameElement::setShouldCollapse(bool collapse) {
+  if (m_shouldCollapse == collapse)
+    return;
+
+  m_shouldCollapse = collapse;
+  if (document().inStyleRecalc())
+    reattachLayoutTree();
+  else
+    lazyReattachIfAttached();
+}
+
 DOMTokenList* HTMLIFrameElement::sandbox() const {
   return m_sandbox.get();
 }
@@ -154,7 +166,8 @@ void HTMLIFrameElement::parseAttribute(
 }
 
 bool HTMLIFrameElement::layoutObjectIsNeeded(const ComputedStyle& style) {
-  return contentFrame() && HTMLElement::layoutObjectIsNeeded(style);
+  return contentFrame() && !m_shouldCollapse &&
+         HTMLFrameElementBase::layoutObjectIsNeeded(style);
 }
 
 LayoutObject* HTMLIFrameElement::createLayoutObject(const ComputedStyle&) {