ozone: Implement zero/one-copy texture for Ozone GBM.

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

Index: ui/ozone/platform/drm/gpu/gbm_buffer.cc
diff --git a/ui/ozone/platform/drm/gpu/gbm_buffer.cc b/ui/ozone/platform/drm/gpu/gbm_buffer.cc
index 3f3704025072f00f6f917fe75d5adc9156dbf7c2..6809b487ae30da20ae68ad5e4f8f53fd42ef070f 100644
--- a/ui/ozone/platform/drm/gpu/gbm_buffer.cc
+++ b/ui/ozone/platform/drm/gpu/gbm_buffer.cc
@@ -51,8 +51,9 @@ scoped_refptr<GbmBuffer> GbmBuffer::CreateBuffer(
   TRACE_EVENT2("drm", "GbmBuffer::CreateBuffer", "device",
                gbm->device_path().value(), "size", size.ToString());
   unsigned flags = GBM_BO_USE_RENDERING;
-  if (scanout)
-    flags |= GBM_BO_USE_SCANOUT;
+  // SCANOUT allocates continuous memory, so better for performance even if
+  // |scanout| is false.
+  flags |= GBM_BO_USE_SCANOUT;
   gbm_bo* bo = gbm_bo_create(gbm->device(), size.width(), size.height(),
                              GetGbmFormatFromBufferFormat(format), flags);
   if (!bo)
@@ -97,4 +98,17 @@ int GbmPixmap::GetDmaBufPitch() {
   return gbm_bo_get_stride(buffer_->bo());
 }
 
+NativePixmap::BufferUsage GbmPixmap::GetBufferUsage() const {
+  return buffer_->GetFramebufferId() ? SCANOUT : MAP;
+}
+
+void* GbmPixmap::Map() {
+  NOTREACHED();
+  return nullptr;
+}
+
+void GbmPixmap::Unmap() {
+  NOTREACHED();
+}
+
 }  // namespace ui