[DevTools] Fix out of process iframes not working on chrome://inspect.

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 846 matching lines @@
       static_cast<RenderFrameHostImpl*>(wc->GetMainFrame());
   DCHECK(host);
   frame_tree_node_ = host->frame_tree_node();
   current_ = std::move(disconnected_);
   SetPending(host);
   CommitPending();
   WebContentsObserver::Observe(WebContents::FromRenderFrameHost(host));
 }
 
 std::string RenderFrameDevToolsAgentHost::GetParentId() {
-  if (IsChildFrame()) {
-    RenderFrameHostImpl* frame_host = current_->host();
+  if (IsChildFrame() && current_) {
+    RenderFrameHostImpl* frame_host = current_->host()->GetParent();
     while (frame_host && !ShouldCreateDevToolsFor(frame_host))
       frame_host = frame_host->GetParent();
     if (frame_host)
       return DevToolsAgentHost::GetOrCreateFor(frame_host)->GetId();
   }
 
   WebContentsImpl* contents = static_cast<WebContentsImpl*>(web_contents());
   if (!contents)
     return "";
   contents = contents->GetOuterWebContents();
@@ skipping 147 matching lines @@
     RenderFrameHost* host) {
   return (current_ && current_->host() == host) ||
       (pending_ && pending_->host() == host);
 }
 
 bool RenderFrameDevToolsAgentHost::IsChildFrame() {
   return current_ && current_->host()->GetParent();
 }
 
 }  // namespace content