Skip memcpy() swizzles in SkPngCodec

src/codec/SkPngCodec.h

Index: src/codec/SkPngCodec.h
diff --git a/src/codec/SkPngCodec.h b/src/codec/SkPngCodec.h
index 95fd61316342f5f46dd875f724e3df755b34b6ca..de81131ff115c26978af90b305bd1149372a7da8 100644
--- a/src/codec/SkPngCodec.h
+++ b/src/codec/SkPngCodec.h
@@ -33,13 +33,13 @@ protected:
     bool onRewind() override;
     uint32_t onGetFillValue(SkColorType) const override;
 
-    // Helper to set up swizzler and color table. Also calls png_read_update_info.
-    Result initializeSwizzler(const SkImageInfo& requestedInfo, const Options&,
+    // Helper to create color table and determine fSrcConfig. Also calls png_read_update_info.
+    Result prepareToDecode(const SkImageInfo& requestedInfo, const Options&,
                               SkPMColor*, int* ctableCount);
-    SkSampler* getSampler(bool createIfNecessary) override {
-        SkASSERT(fSwizzler);
-        return fSwizzler;
-    }
+
+    void initializeSwizzler(const SkImageInfo& requestedInfo, const Options&);
+
+    SkSampler* getSampler(bool createIfNecessary) override;
 
     SkPngCodec(const SkImageInfo&, SkStream*, SkPngChunkReader*, png_structp, png_infop, int, int);