WinForms/WPF/OffScreen - Object reference incorrectly held at CefShutdown

- **What version of the product are you using?**
- Nuget CefSharp.OffScreen version 79.1.35
- CEF `cef_binary_79.1.35+gfebbb4a+chromium-79.0.3945.130_windows64` debug binaries
- **What architecture x86 or x64?**
- At least in x64,
- Though I was able to reproduce with x86 version 75.1.14
- **On what operating system?**
- Win10
- **Are you using `WinForms`, `WPF` or `OffScreen`?**
- OffScreen
- **What steps will reproduce the problem?**
- Using OffScreen, load a page, and as soon as it completes loading, call `Cef.Shutdown()`
- Minimal repro source code is at https://github.com/kiewic/reference-incorrectly-held-at-CefShutdown/tree/version-79
- **Debug** CEF binaries are necessary, since the CEF's `shutdown_checker` implementation is empty in Release versions
- **What is the expected output? What do you see instead?**
- No crash or *debug.log* errors are expected. However, the process crashes [almost every time] after printing the following message:

```
[0208/223134.848:FATAL:shutdown_checker.cc(52)] Check failed: !IsCefShutdown(). Object reference incorrectly held at CefShutdown
[0208/223134.887:FATAL:shutdown_checker.cc(52)] Check failed: !IsCefShutdown(). Object reference incorrectly held at CefShutdown
```

- **Please provide any additional information below.**

The crash callstack is:

```
00 libcef!logging::LogMessage::~LogMessage+0x647 [Y:\work\CEF3_git\chromium\src\base\logging.cc @ 954]
01 libcef!shutdown_checker::AssertNotShutdown+0x78 [Y:\work\CEF3_git\chromium\src\cef\libcef_dll\shutdown_checker.cc @ 54]
02 libcef!CefLifeSpanHandlerCToCpp::OnBeforeClose+0x29 [Y:\work\CEF3_git\chromium\src\cef\libcef_dll\ctocpp\life_span_handler_ctocpp.cc @ 150]
03 libcef!CefBrowserHostImpl::DestroyBrowser+0xf3 [Y:\work\CEF3_git\chromium\src\cef\libcef\browser\browser_host_impl.cc @ 1539]
04 libcef!CefBrowserInfoManager::DestroyAllBrowsers+0x13f [Y:\work\CEF3_git\chromium\src\cef\libcef\browser\browser_info_manager.cc @ 332]
05 libcef!CefContext::FinishShutdownOnUIThread+0x7a [Y:\work\CEF3_git\chromium\src\cef\libcef\browser\context.cc @ 606]
06 libcef!base::OnceCallback::Run+0x61 [Y:\work\CEF3_git\chromium\src\base\callback.h @ 98]
07 libcef!base::TaskAnnotator::RunTask+0x185 [Y:\work\CEF3_git\chromium\src\base\task\common\task_annotator.cc @ 142]
08 libcef!base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWorkImpl+0x1b5 [Y:\work\CEF3_git\chromium\src\base\task\sequence_manager\thread_controller_with_message_pump_impl.cc @ 366]
09 libcef!base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoSomeWork+0x61 [Y:\work\CEF3_git\chromium\src\base\task\sequence_manager\thread_controller_with_message_pump_impl.cc @ 221]
0a libcef!base::MessagePumpForUI::DoRunLoop+0x143 [Y:\work\CEF3_git\chromium\src\base\message_loop\message_pump_win.cc @ 219]
0b libcef!base::MessagePumpWin::Run+0xa4 [Y:\work\CEF3_git\chromium\src\base\message_loop\message_pump_win.cc @ 77]
0c libcef!base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::Run+0x129 [Y:\work\CEF3_git\chromium\src\base\task\sequence_manager\thread_controller_with_message_pump_impl.cc @ 467]
0d libcef!base::RunLoop::Run+0x30e [Y:\work\CEF3_git\chromium\src\base\run_loop.cc @ 158]
0e libcef!CefUIThread::ThreadMain+0x77 [Y:\work\CEF3_git\chromium\src\cef\libcef\common\main_delegate.cc @ 395]
0f libcef!base::`anonymous namespace'::ThreadFunc+0xcc [Y:\work\CEF3_git\chromium\src\base\threading\platform_thread_win.cc @ 105]
10 KERNEL32!BaseThreadInitThunk+0x14 [base\win32\client\thread.c @ 64]
11 ntdll!RtlUserThreadStart+0x21 [minkernel\ntdll\rtlstrt.c @ 1153]
```

But the main thread (thread 0) has already called `CefShutdown`:

```
00 ntdll!ZwWaitForSingleObject+0x14 [minkernel\ntdll\daytona\objfre\amd64\usrstubs.asm @ 211]
01 KERNELBASE!WaitForSingleObjectEx+0x93 [minkernel\kernelbase\synch.c @ 1328]
02 libcef!base::WaitableEvent::Wait+0xab [Y:\work\CEF3_git\chromium\src\base\synchronization\waitable_event_win.cc @ 69]
03 libcef!CefContext::Shutdown+0x10f [Y:\work\CEF3_git\chromium\src\cef\libcef\browser\context.cc @ 481]
04 libcef!CefShutdown+0xb5 [Y:\work\CEF3_git\chromium\src\cef\libcef\browser\context.cc @ 272]
05 CefSharp_Core!DomainBoundILStubClass.IL_STUB_PInvoke()+0x68
06 CefSharp_Core!CefSharp::Cef::Shutdown+0x283 [c:\projects\cefsharp\cefsharp.core\cef.h @ 89]
07 CefSharpOffscreenRepro!CefSharpOffscreenRepro.Program.Main(System.String[])+0x28b*** WARNING: Unable to verify checksum for D:\repos\reference-incorrectly-held-at-CefShutdown\CefSharpOffscreenRepro\bin\x64\Debug\CefSharpOffscreenRepro.exe
[D:\repos\reference-incorrectly-held-at-CefShutdown\CefSharpOffscreenRepro\Program.cs @ 64]
08 CefSharpOffscreenRepro!CefSharpOffscreenRepro.Program.Main(System.String[])+0x1ae
09 clr!CallDescrWorkerInternal+0x83 [f:\dd\ndp\clr\src\vm\amd64\CallDescrWorkerAMD64.asm @ 97]
0a clr!CallDescrWorkerWithHandler+0x4e [f:\dd\ndp\clr\src\vm\callhelpers.cpp @ 89]
0b clr!MethodDescCallSite::CallTargetWorker+0x102 [f:\dd\ndp\clr\src\vm\callhelpers.cpp @ 655]
0c clr!MethodDescCallSite::Call_RetArgSlot+0x5 [f:\dd\ndp\clr\src\vm\callhelpers.h @ 423]
0d clr!RunMain+0x266 [f:\dd\ndp\clr\src\vm\assembly.cpp @ 2659]
0e clr!Assembly::ExecuteMainMethod+0xb7 [f:\dd\ndp\clr\src\vm\assembly.cpp @ 2780]
0f clr!SystemDomain::ExecuteMainMethod+0x643 [f:\dd\ndp\clr\src\vm\appdomain.cpp @ 3755]
10 clr!ExecuteEXE+0x3f [f:\dd\ndp\clr\src\vm\ceemain.cpp @ 3053]
11 clr!_CorExeMainInternal+0xb2 [f:\dd\ndp\clr\src\vm\ceemain.cpp @ 2887]
12 clr!_CorExeMain+0x14 [f:\dd\ndp\clr\src\vm\ceemain.cpp @ 2814]
13 mscoreei!_CorExeMain+0x112 [f:\dd\ndp\clr\src\dlls\shim\shim.cpp @ 6425]
14 MSCOREE!_CorExeMain_Exported+0x6c [onecore\com\netfx\windowsbuilt\shell_shim\v2api.cpp @ 1223]
15 KERNEL32!BaseThreadInitThunk+0x14 [base\win32\client\thread.c @ 64]
16 ntdll!RtlUserThreadStart+0x21 [minkernel\ntdll\rtlstrt.c @ 1153]
```

You can download a mini dump of the crash [here](https://1drv.ms/u/s!AqlYeTdRfiBjhY0K9Gb3jQy_tSwfBw?e=bb3XvZ).

I have already provided the relevant log errors above, but you can find the full *debug.log* [here](https://1drv.ms/u/s!AqlYeTdRfiBjhY0N3snUwJjyIVh5kA?e=bsG1zN).

Even when the repro project has a hardcoded URI, the issue reproduces with any URI.

- **Does this problem also occur in the `CEF` Sample Application**
- N/A