ui: Add gfx::BufferUsage::SCANOUT_CPU_READ_WRITE.

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

 // Copyright 2015 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/drm_thread.h"
 
 #include <gbm.h>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 99 matching lines @@
       static_cast<GbmDevice*>(device_manager_->GetDrmDevice(widget).get());
   DCHECK(gbm);
 
   uint32_t flags = 0;
   switch (usage) {
     case gfx::BufferUsage::GPU_READ:
       break;
     case gfx::BufferUsage::SCANOUT:
       flags = GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING;
       break;
+    case gfx::BufferUsage::SCANOUT_CPU_READ_WRITE:
+      flags = GBM_BO_USE_SCANOUT | GBM_BO_USE_LINEAR;
+      break;
     case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE:
     case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT:
       flags = GBM_BO_USE_LINEAR;
       break;
   }
 
   DrmWindow* window = screen_manager_->GetWindow(widget);
   std::vector<uint64_t> modifiers;
 
   uint32_t fourcc_format = ui::GetFourCCFormatFromBufferFormat(format);
@@ skipping 155 matching lines @@
                                        correction_matrix);
 }
 
 // DrmThread requires a BindingSet instead of a simple Binding because it will
 // be used from multiple threads in multiple processes.
 void DrmThread::AddBinding(ozone::mojom::DeviceCursorRequest request) {
   bindings_.AddBinding(this, std::move(request));
 }
 
 }  // namespace ui