Add ThreadChecker for Ozone X11 GPU.

ui/ozone/platform/x11/x11_surface_factory.h

 // Copyright 2016 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.
 
 #ifndef UI_OZONE_PLATFORM_X11_X11_SURFACE_FACTORY_H_
 #define UI_OZONE_PLATFORM_X11_X11_SURFACE_FACTORY_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "ui/gl/gl_surface.h"
 #include "ui/ozone/public/gl_ozone.h"
 #include "ui/ozone/public/surface_factory_ozone.h"
 
 namespace ui {
 
 // Handles GL initialization and surface/context creation for X11.
 class X11SurfaceFactory : public SurfaceFactoryOzone {
  public:
   X11SurfaceFactory();
   ~X11SurfaceFactory() override;
 
   // SurfaceFactoryOzone:
   std::vector<gl::GLImplementation> GetAllowedGLImplementations() override;
   GLOzone* GetGLOzone(gl::GLImplementation implementation) override;
 
  private:
   std::unique_ptr<GLOzone> glx_implementation_;
   std::unique_ptr<GLOzone> egl_implementation_;
 
+  // X11 doesn't care if things being called from different threads if
+  // XInitThreads() was called. However, GBM does care. This will ensure X11
+  // and GBM behave roughly the same.
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(X11SurfaceFactory);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_X11_X11_SURFACE_FACTORY_H_