1. @DomName('WebGLRenderingContext.getSupportedExtensions')
  2. @DocsEditable()
List<String> getSupportedExtensions()

Source 

@DomName('WebGLRenderingContext.getSupportedExtensions')
@DocsEditable()
List<String> getSupportedExtensions() =>
    _blink.BlinkWebGLRenderingContext.instance
        .getSupportedExtensions_Callback_0_(this);