Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

content/public/browser/navigation_throttle.h

Index: content/public/browser/navigation_throttle.h
diff --git a/content/public/browser/navigation_throttle.h b/content/public/browser/navigation_throttle.h
index ba49aa73a716aa81af9106d7b875df3f18fa26ac..76391291df806961d9e4ad56641014ad15c61256 100644
--- a/content/public/browser/navigation_throttle.h
+++ b/content/public/browser/navigation_throttle.h
@@ -39,6 +39,11 @@ class CONTENT_EXPORT NavigationThrottle {
     // is navigated.
     BLOCK_REQUEST,
 
+    // Blocks a navigation taking place in a subframe, and collapses the frame
+    // owner element in the parent frame (i.e. removes it from the layout). Can
+    // be be returned from WillStartRequest or WillRedirectRequest.

[nasko, 2017/03/01 20:08:05]

nit: Only one "be" needed.

+    BLOCK_REQUEST_AND_COLLAPSE,
+
     // Blocks a navigation due to rules asserted by a response (for instance,
     // embedding restrictions like 'X-Frame-Options'). This result will only
     // be returned from WillProcessResponse.