ui: Revert gfx::BufferUsage::SCANOUT to gfx::BufferUsage::GPU_READ_WRITE change.

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

Index: ui/ozone/platform/drm/gpu/drm_thread.cc
diff --git a/ui/ozone/platform/drm/gpu/drm_thread.cc b/ui/ozone/platform/drm/gpu/drm_thread.cc
index 19ecdfbeb68a9246084b00988c317f7beab9679a..901dedb08c7c0aa19398ed49293842dd7a6f6703 100644
--- a/ui/ozone/platform/drm/gpu/drm_thread.cc
+++ b/ui/ozone/platform/drm/gpu/drm_thread.cc
@@ -34,7 +34,7 @@ class GbmBufferGenerator : public ScanoutBufferGenerator {
                                       const gfx::Size& size) override {
     scoped_refptr<GbmDevice> gbm(static_cast<GbmDevice*>(drm.get()));
     return GbmBuffer::CreateBuffer(gbm, format, size,
-                                   gfx::BufferUsage::GPU_READ_WRITE);
+                                   gfx::BufferUsage::SCANOUT);
   }
 
  protected: