This enforces stricter rules on the SkSL at effect creation time, and
ensures it's valid as an SkShader (vs. an SkColorFilter). Also updated
some SkSL that was already (or would become) illegal:
- Child shaders must be declared 'uniform', not 'in'
- sampling a child requires coordinates
Bug: skia:11813
Change-Id: I743b985b5012723186a43e58e9e3ccf29d809d2b
(cherry picked from commit 7556777511b46a0c1a4cdab55d8ba59d99f7c328)
64ee324b93