void reset([Matrix matrix, num alpha, BlendMode blendMode ])

Source 

void reset([Matrix matrix, num alpha, BlendMode blendMode]) {

  _currentContextState = _firstContextState;
  _currentContextState.matrix.identity();
  _currentContextState.alpha = 1.0;
  _currentContextState.blendMode = BlendMode.NORMAL;

  if (matrix is Matrix) _firstContextState.matrix.copyFrom(matrix);
  if (alpha is num) _firstContextState.alpha = alpha;
  if (blendMode is BlendMode) _firstContextState.blendMode = blendMode;
}