1. DomName('WebGL2RenderingContext.beginTransformFeedback')
  2. DocsEditable()
  3. Experimental()
void beginTransformFeedback(int primitiveMode)

Source 

@DomName('WebGL2RenderingContext.beginTransformFeedback')
@DocsEditable()
@Experimental() // untriaged
void beginTransformFeedback(int primitiveMode) => _blink.BlinkWebGL2RenderingContext.instance.beginTransformFeedback_Callback_1_(this, primitiveMode);