We don't use boxBlurY.

src/effects/SkBlurImageFilter.cpp

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkBlurImageFilter.h"
 #include "SkColorPriv.h"
@@ skipping 185 matching lines @@
     }
 
     offset->fX = srcBounds.fLeft;
     offset->fY = srcBounds.fTop;
     srcBounds.offset(-srcOffset);
     const SkPMColor* s = src.getAddr32(srcBounds.left(), srcBounds.top());
     SkPMColor* t = temp.getAddr32(0, 0);
     SkPMColor* d = dst->getAddr32(0, 0);
     int w = dstBounds.width(), h = dstBounds.height();
     int sw = src.rowBytesAsPixels();
-    SkBoxBlurProc boxBlurX, boxBlurY, boxBlurXY, boxBlurYX;
-    if (!SkBoxBlurGetPlatformProcs(&boxBlurX, &boxBlurY, &boxBlurXY, &boxBlurYX)) {
+    SkBoxBlurProc boxBlurX, boxBlurXY, boxBlurYX;
+    if (!SkBoxBlurGetPlatformProcs(&boxBlurX, &boxBlurXY, &boxBlurYX)) {
         boxBlurX = boxBlur<kX, kX>;
-        boxBlurY = boxBlur<kY, kY>;
         boxBlurXY = boxBlur<kX, kY>;
         boxBlurYX = boxBlur<kY, kX>;
     }
 
     if (kernelSizeX > 0 && kernelSizeY > 0) {
         boxBlurX(s,  sw, t, kernelSizeX,  lowOffsetX,  highOffsetX, w, h);
         boxBlurX(t,  w,  d, kernelSizeX,  highOffsetX, lowOffsetX,  w, h);
         boxBlurXY(d, w,  t, kernelSizeX3, highOffsetX, highOffsetX, w, h);
         boxBlurX(t,  h,  d, kernelSizeY,  lowOffsetY,  highOffsetY, h, w);
         boxBlurX(d,  h,  t, kernelSizeY,  highOffsetY, lowOffsetY,  h, w);
@@ skipping 75 matching lines @@
     str->appendf("SkBlurImageFilter: (");
     str->appendf("sigma: (%f, %f) input (", fSigma.fWidth, fSigma.fHeight);
 
     if (this->getInput(0)) {
         this->getInput(0)->toString(str);
     }
 
     str->append("))");
 }
 #endif