A kDefault_Flag = 0 value has been added to the SkSurfaceProps::Flags enum. This is just a self-documenting zero-value that aims to improve code readability, e.g.:

// The two lines below are equivalent.

SkSurfaceProps(/* surfaceFlags= */ 0, kRGB_H_SkPixelGeometry);

SkSurfaceProps(SkSurfaceProps::kDefault_Flag, kRGB_H_SkPixelGeometry);