Route export storage hooks through platform services

src/node_panel_brush.cpp

@@ -9,8 +9,6 @@
 
 #ifdef __APPLE__
 #include <Foundation/Foundation.h>
-#elif __WEB__
-void webgl_sync();
 #endif
 
 #include "canvas.h"
@@ -244,9 +242,7 @@ bool NodePanelBrush::save()
         }
         f.write((char*)sw.m_data.data(), sw.m_data.size());
         f.close();
-#if __WEB__
-        webgl_sync();
-#endif
+        App::I->flush_platform_storage();
         return true;
     }
     return false;