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 34740ca51a8fb503e071098ac5ccbc0881f2c7e4..b6db7c296b7f516ddf75646fa4abc1540d5e4e92 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.

[nasko, 2017/04/20 15:53:40]

nit: s/<iframe>/frame/ as I think we use the same object and code for frameset,
which is rarely used, but exists.

[engedy, 2017/04/28 13:43:59]

They share a base class (HTMLFrameElementBase), but they are implemented as
separate classes in Blink.

For historical reasons, we ignore `display: none` for <frame> elements (starting
with the initial revision [1] until today [2]), so I wanted to be consistent
with that and implement collapsing for <iframe> elements only.

I have added a test for good measure.

[1]:
https://chromium.googlesource.com/chromium/src/+blame/d869b93fe74f4d6cb2dd6f6...

[2]:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/html/HTML...

+  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,