Fix incorrect swizzle on BGRA platforms in filterColor4f path

src/core/SkPM4f.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPM4f_DEFINED
 #define SkPM4f_DEFINED
 
@@ skipping 32 matching lines @@
         return pm;
     }
     static SkPM4f FromF16(const uint16_t[4]);
     static SkPM4f FromPMColor(SkPMColor);
 
     Sk4f to4f() const { return Sk4f::Load(fVec); }
     Sk4f to4f_rgba() const { return this->to4f(); }
     Sk4f to4f_bgra() const { return swizzle_rb(this->to4f()); }
     Sk4f to4f_pmorder() const { return swizzle_rb_if_bgra(this->to4f()); }
 
+    SkPMColor toPMColor() const {
+        Sk4f value = swizzle_rb_if_bgra(this->to4f());
+        SkPMColor result;
+        SkNx_cast<uint8_t>(value * Sk4f(255) + Sk4f(0.5f)).store(&result);
+        return result;
+    }
+
     void toF16(uint16_t[4]) const;
     uint64_t toF16() const; // 4 float16 values packed into uint64_t
 
     SkColor4f unpremul() const;
 
 #ifdef SK_DEBUG
     void assertIsUnit() const;
 #else
     void assertIsUnit() const {}
 #endif
 };
 
 typedef SkPM4f (*SkXfermodeProc4f)(const SkPM4f& src, const SkPM4f& dst);
 
 #endif