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).

libcef/browser/osr/browser_platform_delegate_osr.cc

@@ -13,7 +13,7 @@
 #include "libcef/browser/osr/web_contents_view_osr.h"
 #include "libcef/common/drag_data_impl.h"
 
-#include "base/message_loop/message_loop_current.h"
+#include "base/task/current_thread.h"
 #include "content/browser/renderer_host/render_widget_host_input_event_router.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/render_view_host.h"
@@ -482,7 +482,7 @@ void CefBrowserPlatformDelegateOsr::StartDragging(
     CefRefPtr<CefDragDataImpl> drag_data(
         new CefDragDataImpl(drop_data, cef_image, cef_image_pos));
     drag_data->SetReadOnly(true);
-    base::MessageLoopCurrent::ScopedNestableTaskAllower allow;
+    base::CurrentThread::ScopedNestableTaskAllower allow;
     handled = handler->StartDragging(
         browser_, drag_data.get(),
         static_cast<CefRenderHandler::DragOperationsMask>(allowed_ops),