From 3c0a4410ad50ec2b4559edcf1b0926ad27c10728 Mon Sep 17 00:00:00 2001
From: Marshall Greenblatt <magreenblatt@gmail.com>
Date: Wed, 9 Jun 2021 16:54:50 -0400
Subject: [PATCH] Fix crash if a frame is detached before the attach message
 arrives (see issue #2421)

This reproduced on Mac with ResourceRequestHandlerTest.BasicStandardUnhandledModifyBeforeResourceLoad
---
 libcef/browser/frame_host_impl.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libcef/browser/frame_host_impl.cc b/libcef/browser/frame_host_impl.cc
index dfad616ea..ab3c16d07 100644
--- a/libcef/browser/frame_host_impl.cc
+++ b/libcef/browser/frame_host_impl.cc
@@ -559,6 +559,12 @@ void CefFrameHostImpl::SendMessage(const std::string& name,
 void CefFrameHostImpl::FrameAttached() {
   CEF_REQUIRE_UIT();
 
+  auto browser_info = GetBrowserInfo();
+  if (!browser_info) {
+    // Already Detached.
+    return;
+  }
+
   DCHECK(!is_attached_);
   if (!is_attached_) {
     is_attached_ = true;
@@ -571,7 +577,7 @@ void CefFrameHostImpl::FrameAttached() {
       queued_actions_.pop();
     }
 
-    GetBrowserInfo()->MaybeExecuteFrameNotification(base::BindOnce(
+    browser_info->MaybeExecuteFrameNotification(base::BindOnce(
         [](CefRefPtr<CefFrameHostImpl> self,
            CefRefPtr<CefFrameHandler> handler) {
           if (auto browser = self->GetBrowserHostBase()) {