Use threshold of 1 texture coord value per pixel w/ nearest neighbor.

src/effects/SkAlphaThresholdFilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAlphaThresholdFilter.h"
 #include "SkBitmap.h"
 #include "SkReadBuffer.h"
@@ skipping 69 matching lines @@
     virtual GrGLFragmentProcessor* createGLInstance() const SK_OVERRIDE;
 
 private:
     AlphaThresholdEffect(GrTexture* texture,
                          GrTexture* maskTexture,
                          float innerThreshold,
                          float outerThreshold)
         : fInnerThreshold(innerThreshold)
         , fOuterThreshold(outerThreshold)
         , fImageCoordTransform(kLocal_GrCoordSet,
-                               GrCoordTransform::MakeDivByTextureWHMatrix(texture), texture)
+                               GrCoordTransform::MakeDivByTextureWHMatrix(texture), texture,
+                               GrTextureParams::kNone_FilterMode)
         , fImageTextureAccess(texture)
         , fMaskCoordTransform(kLocal_GrCoordSet,
-                              GrCoordTransform::MakeDivByTextureWHMatrix(maskTexture), maskTexture)
+                              GrCoordTransform::MakeDivByTextureWHMatrix(maskTexture), maskTexture,
+                              GrTextureParams::kNone_FilterMode)
         , fMaskTextureAccess(maskTexture) {
         this->initClassID<AlphaThresholdEffect>();
         this->addCoordTransform(&fImageCoordTransform);
         this->addTextureAccess(&fImageTextureAccess);
         this->addCoordTransform(&fMaskCoordTransform);
         this->addTextureAccess(&fMaskTextureAccess);
     }
 
     virtual bool onIsEqual(const GrFragmentProcessor&) const SK_OVERRIDE;
 
@@ skipping 265 matching lines @@
                                                   (U8CPU)(SkColorGetG(source) * scale),
                                                   (U8CPU)(SkColorGetB(source) * scale));
                 }
             }
             dptr[y * dst->width() + x] = output_color;
         }
     }
 
     return true;
 }