Fix bug in filterSpan4f - read the source, rather than the dest

src/core/SkColorFilter.cpp

 /*
  * Copyright 2006 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 "SkColorFilter.h"
 #include "SkReadBuffer.h"
 #include "SkRefCnt.h"
@@ skipping 19 matching lines @@
 bool SkColorFilter::asComponentTable(SkBitmap*) const {
     return false;
 }
 
 #if SK_SUPPORT_GPU
 sk_sp<GrFragmentProcessor> SkColorFilter::asFragmentProcessor(GrContext*) const {
     return nullptr;
 }
 #endif
 
-void SkColorFilter::filterSpan4f(const SkPM4f[], int count, SkPM4f span[]) const {
+void SkColorFilter::filterSpan4f(const SkPM4f src[], int count, SkPM4f result[]) const {
     const int N = 128;
     SkPMColor tmp[N];
     while (count > 0) {
         int n = SkTMin(count, N);
         for (int i = 0; i < n; ++i) {
-            SkNx_cast<uint8_t>(Sk4f::Load(span[i].fVec) * Sk4f(255) + Sk4f(0.5f)).store(&tmp[i]);
+            SkNx_cast<uint8_t>(Sk4f::Load(src[i].fVec) * Sk4f(255) + Sk4f(0.5f)).store(&tmp[i]);
         }
         this->filterSpan(tmp, n, tmp);
         for (int i = 0; i < n; ++i) {
-            span[i] = SkPM4f::FromPMColor(tmp[i]);
+            result[i] = SkPM4f::FromPMColor(tmp[i]);
         }
-        span += n;
+        src += n;
+        result += n;
         count -= n;
     }
 }
 
 SkColor SkColorFilter::filterColor(SkColor c) const {
     SkPMColor dst, src = SkPreMultiplyColor(c);
     this->filterSpan(&src, 1, &dst);
     return SkUnPreMultiply::PMColorToColor(dst);
 }
 
@@ skipping 114 matching lines @@
     }
     return sk_sp<SkColorFilter>(new SkComposeColorFilter(std::move(outer), std::move(inner),count));
 }
 
 #include "SkModeColorFilter.h"
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkColorFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkComposeColorFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkModeColorFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END