Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

third_party/WebKit/Source/core/frame/FrameOwner.h

Index: third_party/WebKit/Source/core/frame/FrameOwner.h
diff --git a/third_party/WebKit/Source/core/frame/FrameOwner.h b/third_party/WebKit/Source/core/frame/FrameOwner.h
index 6a2a91401b5b39045c7bc04ffdacf2f0d4258622..aa3362849efa3dab53210113381a87ff1376b183 100644
--- a/third_party/WebKit/Source/core/frame/FrameOwner.h
+++ b/third_party/WebKit/Source/core/frame/FrameOwner.h
@@ -39,6 +39,10 @@ class CORE_EXPORT FrameOwner : public GarbageCollectedMixin {
   virtual bool canRenderFallbackContent() const = 0;
   virtual void renderFallbackContent() = 0;
 
+  // Collapses the frame owner, i.e. removes it from the layout of the parent
+  // frame if the owner is an <iframe> element.
+  virtual void setShouldCollapse(bool) {}
+
   // Returns the 'name' content attribute value of the browsing context
   // container.
   // https://html.spec.whatwg.org/multipage/browsers.html#browsing-context-container