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 abc23579cabd91dcd471277b3e78c469d4686a4d..ff51dc226ecfd970d707aef8b80e389bc538e980 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -984,6 +984,27 @@ void RenderFrameHostManager::OnEnforceInsecureRequestPolicy(
   }
 }
 
+void RenderFrameHostManager::OnDidUpdateFrameOwnerCollapsedState(
+    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 site instance 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.

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

Does this mean that if we start a request for which we want to collapse the
frame, we will collapse the current frame, even before we actually get a
response for the request?

[engedy, 2017/01/18 23:37:14]

Yep, that's the plan.

+  DCHECK(current_frame_host());
+  if (current_frame_host()->GetSiteInstance() == parent_site_instance) {
+    current_frame_host()->Send(new FrameMsg_CollapseFrameOwner(
+        current_frame_host()->GetRoutingID(), collapsed));
+  } else {
+    RenderFrameProxyHost* proxy_to_parent = GetProxyToParent();
+    proxy_to_parent->Send(new FrameMsg_CollapseFrameOwner(
+        proxy_to_parent->GetRoutingID(), collapsed));
+  }
+}
+
 void RenderFrameHostManager::OnDidUpdateFrameOwnerProperties(
     const FrameOwnerProperties& properties) {
   if (!SiteIsolationPolicy::AreCrossProcessFramesPossible())