Fix GrDrawContextPriv::stencilRect Updates stencilRect to not call getFillRectBatch. This method can return a batch that uses coverage AA, which isn't appropriate for stencil draws. BUG=skia: GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2057613003 Review-Url: https://codereview.chromium.org/2057613003