class OpacityShapeTest_PremultipliedTexture_Test

We draw the following scene:

+--------+---------+---------+---------+

| | |

| | |

| | |

+ Cyan(25%) | |

| (0, 0.25, 0.25, 0.25) | |

| | |

| | |

+ | |

| | |

| | |

| | |

+----------------------------+ |

| Fuchsia |

| (1, 0, 1, 1) |

| |

+--------+---------+---------+---------+

The Cyan rectangle uses a premultiplied alpha texture, and it

is over the white background.

9/16 of the area should be (0.75, 0.25, 1, 1);

7/16 of the area should be (1, 0, 1, 1);