[Reland] Repeating SkBitmapProcState rounding bias

src/core/SkBitmapProcState.cpp

Index: src/core/SkBitmapProcState.cpp
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index 487bd80402609f454b894e5e124eb5d8eb20c9eb..9c58cc14414407487bc777d07bda6d88ae3eb3c3 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -820,15 +820,10 @@ void  Clamp_S32_opaque_D32_nofilter_DX_shaderproc(const SkBitmapProcState& s, in
     SkFractionalInt fx;
     int dstY;
     {
-        SkPoint pt;
-        s.fInvProc(s.fInvMatrix, SkIntToScalar(x) + SK_ScalarHalf, SkIntToScalar(y) + SK_ScalarHalf,
-                   &pt);
-        fx = SkScalarToFractionalInt(pt.fY)
-            + bitmap_sampler_inv_bias(s.fInvMatrix.getScaleY());
+        const SkBitmapProcStateAutoMapper mapper(s, x, y);
         const unsigned maxY = s.fPixmap.height() - 1;
-        dstY = SkClampMax(SkFractionalIntToInt(fx), maxY);
-        fx = SkScalarToFractionalInt(pt.fX)
-            + bitmap_sampler_inv_bias(s.fInvMatrix.getScaleX());
+        dstY = SkClampMax(SkFractionalIntToInt(mapper.y()), maxY);
+        fx = mapper.x();
     }
 
     const SkPMColor* SK_RESTRICT src = s.fPixmap.addr32(0, dstY);