Fix incorrect swizzle on BGRA platforms in filterColor4f path

src/core/SkPM4f.h

Index: src/core/SkPM4f.h
diff --git a/src/core/SkPM4f.h b/src/core/SkPM4f.h
index e99ddccd8effac93898897df523042ac38a7ccba..f983101f41f573b2fccfed31209b56bc790f3f0e 100644
--- a/src/core/SkPM4f.h
+++ b/src/core/SkPM4f.h
@@ -50,6 +50,13 @@ struct SkPM4f {
     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