Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

content/browser/frame_host/render_frame_host_manager.h

Index: content/browser/frame_host/render_frame_host_manager.h
diff --git a/content/browser/frame_host/render_frame_host_manager.h b/content/browser/frame_host/render_frame_host_manager.h
index 5281069d85a2e910b1ccf6564b454100bdbd7e86..24810ed15e4d3b918dad1dcb88e9dd03f77a7d84 100644
--- a/content/browser/frame_host/render_frame_host_manager.h
+++ b/content/browser/frame_host/render_frame_host_manager.h
@@ -431,6 +431,12 @@ class CONTENT_EXPORT RenderFrameHostManager
   // when the frame changes its setting.
   void OnEnforceInsecureRequestPolicy(blink::WebInsecureRequestPolicy policy);
 
+  // Called when the client changes whether the frame's owner element in the
+  // embedder document should be collapsed, that is, remove from the layout as
+  // if it did not exist. Never called for main frames. Only has an effect for
+  // <iframe> owner elements.
+  void OnDidChangeCollapsedState(bool collapsed);
+
   // Called on a frame to notify it that its out-of-process parent frame
   // changed a property (such as allowFullscreen) on its <iframe> element.
   // Sends updated FrameOwnerProperties to the RenderFrame and to all proxies,