Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

content/browser/frame_host/render_frame_host_manager.cc

Index: content/browser/frame_host/render_frame_host_manager.cc
diff --git a/content/browser/frame_host/render_frame_host_manager.cc b/content/browser/frame_host/render_frame_host_manager.cc
index 5ae522b0a7b448c1cf8ab395d06544110703e08e..b61d6a1b1fc134f31279c83113800c8e9ecf3421 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -930,6 +930,26 @@ void RenderFrameHostManager::OnEnforceInsecureRequestPolicy(
   }
 }
 
+void RenderFrameHostManager::OnDidChangeCollapsedState(bool collapsed) {
+  DCHECK(frame_tree_node_->parent());
+  SiteInstance* parent_site_instance =
+      frame_tree_node_->parent()->current_frame_host()->GetSiteInstance();
+
+  // There will be no proxy to represent the pending or speculative RFHs in the
+  // parent's SiteInstance until the provisional load is committed, but the old
+  // RFH is not swapped out before that happens either, so we can talk to the
+  // FrameOwner in the parent via the child's current RenderFrame at any time.
+  DCHECK(current_frame_host());
+  if (current_frame_host()->GetSiteInstance() == parent_site_instance) {
+    current_frame_host()->Send(
+        new FrameMsg_Collapse(current_frame_host()->GetRoutingID(), collapsed));
+  } else {
+    RenderFrameProxyHost* proxy_to_parent = GetProxyToParent();

[alexmos, 2017/04/11 06:00:29]

optional: you could just use GetRenderFrameProxyHost(parent_site_instance) here
to avoid repeating the parent SiteInstance lookup.  (I also find our name for
GetProxyToParent pretty confusing :) )

[engedy, 2017/04/11 08:06:17]

Nice, done!

+    proxy_to_parent->Send(
+        new FrameMsg_Collapse(proxy_to_parent->GetRoutingID(), collapsed));
+  }
+}
+
 void RenderFrameHostManager::OnDidUpdateFrameOwnerProperties(
     const FrameOwnerProperties& properties) {
   if (!SiteIsolationPolicy::AreCrossProcessFramesPossible())