Use SkBitmapProcStateAutoMapper for filter samplers also

src/core/SkBitmapProcState_shaderproc.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMathPriv.h"
 
 #define SCALE_FILTER_NAME       MAKENAME(_filter_DX_shaderproc)
@@ skipping 13 matching lines @@
 
     const unsigned maxX = s.fPixmap.width() - 1;
     const SkFixed oneX = s.fFilterOneX;
     const SkFixed dx = s.fInvSx;
     SkFixed fx;
     const SRCTYPE* SK_RESTRICT row0;
     const SRCTYPE* SK_RESTRICT row1;
     unsigned subY;
 
     {
-        SkPoint pt;
-        s.fInvProc(s.fInvMatrix, SkIntToScalar(x) + SK_ScalarHalf,
-                   SkIntToScalar(y) + SK_ScalarHalf, &pt);
-        SkFixed fy = SkScalarToFixed(pt.fY) - (s.fFilterOneY >> 1);
+        const SkBitmapProcStateAutoMapper mapper(s, x, y);
+        SkFixed fy = SkFractionalIntToFixed(mapper.y());
         const unsigned maxY = s.fPixmap.height() - 1;
         // compute our two Y values up front
         subY = TILEY_LOW_BITS(fy, maxY);
         int y0 = TILEY_PROCF(fy, maxY);
         int y1 = TILEY_PROCF((fy + s.fFilterOneY), maxY);
 
         const char* SK_RESTRICT srcAddr = (const char*)s.fPixmap.addr();
         size_t rb = s.fPixmap.rowBytes();
         row0 = (const SRCTYPE*)(srcAddr + y0 * rb);
         row1 = (const SRCTYPE*)(srcAddr + y1 * rb);
         // now initialize fx
-        fx = SkScalarToFixed(pt.fX) - (oneX >> 1);
+        fx = SkFractionalIntToFixed(mapper.x());
     }
 
 #ifdef PREAMBLE
     PREAMBLE(s);
 #endif
 
     do {
         unsigned subX = TILEX_LOW_BITS(fx, maxX);
         unsigned x0 = TILEX_PROCF(fx, maxX);
         unsigned x1 = TILEX_PROCF((fx + oneX), maxX);
@@ skipping 22 matching lines @@
 #undef TILEY_LOW_BITS
 #undef MAKENAME
 #undef SRCTYPE
 #undef CHECKSTATE
 #undef SRC_TO_FILTER
 #undef FILTER_TO_DST
 #undef PREAMBLE
 #undef POSTAMBLE
 
 #undef SCALE_FILTER_NAME