Add NativePixmapHandle type & interface for exporting them

ui/ozone/platform/cast/surface_factory_cast.cc

Index: ui/ozone/platform/cast/surface_factory_cast.cc
diff --git a/ui/ozone/platform/cast/surface_factory_cast.cc b/ui/ozone/platform/cast/surface_factory_cast.cc
index e9aea7d19f5d1642e62096289737a2755fc165ca..e0a728feafa535287c4d0f91ce2110829b186dc2 100644
--- a/ui/ozone/platform/cast/surface_factory_cast.cc
+++ b/ui/ozone/platform/cast/surface_factory_cast.cc
@@ -211,6 +211,9 @@ scoped_refptr<NativePixmap> SurfaceFactoryCast::CreateNativePixmap(
     scoped_refptr<NativePixmap> GetScaledPixmap(gfx::Size new_size) override {
       return nullptr;
     }
+    gfx::NativePixmapHandle ExportHandle() override {
+      return gfx::NativePixmapHandle();
+    }
 
    private:
     ~CastPixmap() override {}