Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

content/browser/frame_host/frame_tree_node.h

Index: content/browser/frame_host/frame_tree_node.h
diff --git a/content/browser/frame_host/frame_tree_node.h b/content/browser/frame_host/frame_tree_node.h
index 701787120d6ce6863e0ea4672ceeeb46e037e361..e772990570fb9bd6841851fdb642b7c2f382f878 100644
--- a/content/browser/frame_host/frame_tree_node.h
+++ b/content/browser/frame_host/frame_tree_node.h
@@ -137,6 +137,15 @@ class CONTENT_EXPORT FrameTreeNode {
     return has_committed_real_load_;
   }
 
+  // Returns whether the frame's owner element in the parent frame is collapsed
+  // as per request by the client, i.e. it should not appear in the layout.
+  bool is_frame_owner_collapsed() const { return is_frame_owner_collapsed_; }
+
+  // Sets whether to collapse, i.e. exclude from the layout, the frame's owner
+  // element in the parent frame. Not applicable to main frames, and will have
+  // no effect unless the child frame is embedded using an <iframe> element.

[clamy, 2017/01/18 15:10:55]

It's not very clear to me while reading this description what this means. Does
it mean that the parent frame won't show or this one?

[engedy, 2017/02/17 18:09:25]

I have done some wordsmithing, please take another look.

+  void SetFrameOwnerCollapsedState(bool collapsed);
+
   // Returns the origin of the last committed page in this frame.
   // WARNING: To get the last committed origin for a particular
   // RenderFrameHost, use RenderFrameHost::GetLastCommittedOrigin() instead,
@@ -346,6 +355,11 @@ class CONTENT_EXPORT FrameTreeNode {
   // about:blank page.
   bool has_committed_real_load_;
 
+  // Whether the frame's owner element in the parent frame is collapsed, i.e. it
+  // does not appear in the layout. Always false for main frames, and has have
+  // no effect unless the child frame is embedded using an <iframe> element.
+  bool is_frame_owner_collapsed_;
+
   // Track information that needs to be replicated to processes that have
   // proxies for this frame.
   FrameReplicationState replication_state_;