Add bilerp filtering.

gm/SkLinearBitmapPipelineGM.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkCanvas.h"
 #include "SkColor.h"
@@ skipping 86 matching lines @@
     SkPixmap pmdst;
     bmdst.peekPixels(&pmdst);
 
     SkPM4f* dstBits = new SkPM4f[ir.width()];
     SkImageInfo info = SkImageInfo::MakeN32(ir.width(), ir.height(), kPremul_SkAlphaType);
 
     SkMatrix inv;
     bool trash = mat->invert(&inv);
     sk_ignore_unused_variable(trash);
 
+    SkFilterQuality filterQuality;
+    if (useBilerp) {
+        filterQuality = SkFilterQuality::kLow_SkFilterQuality;
+    } else {
+        filterQuality = SkFilterQuality::kNone_SkFilterQuality;
+    }
+
     uint32_t flags = 0;
     //if (kSRGB_SkColorProfileType == profile) {
         //flags |= SkXfermode::kDstIsSRGB_PM4fFlag;
     //}
     const SkXfermode::PM4fState state { nullptr, flags };
     auto procN = SkXfermode::GetPM4fProcN(SkXfermode::kSrcOver_Mode, flags);
 
     SkLinearBitmapPipeline pipeline{
-            inv, SkShader::kClamp_TileMode, SkShader::kClamp_TileMode, info, pmsrc.addr32()};
-
+            inv, filterQuality,
+            SkShader::kClamp_TileMode, SkShader::kClamp_TileMode,
+            info, pmsrc.addr32()};
 
     for (int y = 0; y < ir.height(); y++) {
         pipeline.shadeSpan4f(0, y, dstBits, ir.width());
         procN(state, pmdst.writable_addr32(0, y), dstBits, ir.width(), nullptr);
     }
 
     delete [] dstBits;
 
     canvas->drawBitmap(bmdst, r.left(), r.top(), nullptr);
 }
@@ skipping 55 matching lines @@
             }
             canvas->restore();
             canvas->translate(0, H + 20);
         }
         canvas->restore();
         canvas->translate(0, (H + 20) * SK_ARRAY_COUNT(mats));
         if (useBilerp) break;
         useBilerp = true;
     }
 }