Fix black screen when switching primary display without bounds change

ui/ozone/platform/drm/gpu/gbm_buffer_base.cc

 // Copyright 2014 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.
 
 #include "ui/ozone/platform/drm/gpu/gbm_buffer_base.h"
 
 #include <gbm.h>
 
 #include "base/logging.h"
 #include "ui/ozone/platform/drm/common/drm_util.h"
@@ skipping 39 matching lines @@
 
 gfx::Size GbmBufferBase::GetSize() const {
   return gfx::Size(gbm_bo_get_width(bo_), gbm_bo_get_height(bo_));
 }
 
 uint32_t GbmBufferBase::GetFramebufferPixelFormat() const {
   DCHECK(framebuffer_);
   return framebuffer_pixel_format_;
 }
 
+const DrmDevice* GbmBufferBase::GetDrmDevice() const {
+  return drm_.get();
+}
+
 bool GbmBufferBase::RequiresGlFinish() const {
   return !drm_->is_primary_device();
 }
 
 }  // namespace ui