Victor Choueiri d57cc44f05 Add SweepGradient (#17368)
This PR adds a SweepGradient class, extending Gradient to expose the engine's ui.Gradient.sweep shader.

Similar to LinearGradient and RadialGradient - SweepGradients can be used in a BoxDecoration or passed to a Paint's shader.
2018-05-30 15:18:17 -07:00
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2018-05-30 15:18:17 -07:00