[DevTools] Auto-attach to cross-process subframes under experiment.

content/browser/devtools/render_frame_devtools_agent_host.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/devtools/render_frame_devtools_agent_host.h"
 
 #include <tuple>
 #include <utility>
 
 #include "base/guid.h"
@@ skipping 644 matching lines @@
   if (!IsBrowserSideNavigationEnabled())
     return;
   DCHECK(current_);
   navigating_handles_.insert(navigation_handle);
   DCHECK(CheckConsistency());
 }
 
 void RenderFrameDevToolsAgentHost::RenderFrameHostChanged(
     RenderFrameHost* old_host,
     RenderFrameHost* new_host) {
+  target_handler_->UpdateFrames();
+
   if (IsBrowserSideNavigationEnabled())
     return;
 
   DCHECK(!pending_ || pending_->host() != old_host);
   if (!current_ || current_->host() != old_host) {
     DCHECK(CheckConsistency());
     return;
   }
 
   // AboutToNavigateRenderFrame was not called for renderer-initiated
@@ skipping 396 matching lines @@
     RenderFrameHost* host) {
   return (current_ && current_->host() == host) ||
       (pending_ && pending_->host() == host);
 }
 
 bool RenderFrameDevToolsAgentHost::IsChildFrame() {
   return current_ && current_->host()->GetParent();
 }
 
 }  // namespace content