Update to Chromium version 86.0.4240.0 (#800218)

- CefURLRequest::Create is no longer supported in the renderer process
  (see https://crbug.com/891872). Use CefFrame::CreateURLRequest instead.
- Mac platform definitions have been changed from `MACOSX` to `MAC`
  (see https://crbug.com/1105907) and related CMake macro names have
  been updated. The old `OS_MACOSX` define is still set in code and CMake
  for backwards compatibility.
- Linux ARM build is currently broken (see https://crbug.com/1123214).

tests/shared/browser/client_app_browser.cc

@@ -47,7 +47,7 @@ void ClientAppBrowser::OnBeforeCommandLineProcessing(
       command_line->AppendSwitch("disable-gpu-shader-disk-cache");
     }
 
-#if defined(OS_MACOSX)
+#if defined(OS_MAC)
     // Disable the toolchain prompt on macOS.
     command_line->AppendSwitch("use-mock-keychain");
 #endif