Comment describes it: Unless we do something to confuse their optimizer,
they will (incorrectly) deduce that uniform opaque color (modulated only
by a texture fetch) is always going to remain opaque. Then they skip
inserting their shader based blending code, turning SrcOver into Src.
Doing a max against zero is enough to squelch the optimization.
Bug: skia:
Change-Id: I74676cebb0b0c8d121da868dd8a88050e0cfcc0d
Reviewed-on: https://skia-review.googlesource.com/17924
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
ac1e4964e7