ozone: Introduce ClientPixmap and ClientPixmapFactory for non-GPU processes.

ui/ozone/platform/drm/host/drm_display_host_manager.cc

Index: ui/ozone/platform/drm/host/drm_display_host_manager.cc
diff --git a/ui/ozone/platform/drm/host/drm_display_host_manager.cc b/ui/ozone/platform/drm/host/drm_display_host_manager.cc
index 0305559fbe6dc5f2be5afa5377042504b7fa6f35..3d7b7b4f245c81d4646f4651f7f9699753fa66e9 100644
--- a/ui/ozone/platform/drm/host/drm_display_host_manager.cc
+++ b/ui/ozone/platform/drm/host/drm_display_host_manager.cc
@@ -155,6 +155,23 @@ DrmDisplayHostManager::DrmDisplayHostManager(
   }
 }
 
+base::FileDescriptor DrmDisplayHostManager::DupVgemFd() {
+  if (vgem_card_path_.empty())
+    return base::FileDescriptor();
+
+  int duped_handle = -1;
+  {
+    base::ThreadRestrictions::ScopedAllowIO allow_io;
+    duped_handle = HANDLE_EINTR(dup(vgem_card_device_file_.get()));
+  }
+  if (duped_handle < 0) {
+    PLOG(ERROR) << "dup() failed.";
+    return base::FileDescriptor();
+  }
+
+  return base::FileDescriptor(duped_handle, true);
+}
+
 DrmDisplayHostManager::~DrmDisplayHostManager() {
   device_manager_->RemoveObserver(this);
   proxy_->UnregisterHandler(this);