SkSwizzler: Factor skipping zeros out into a helper function.

src/codec/SkSwizzler.h

Index: src/codec/SkSwizzler.h
diff --git a/src/codec/SkSwizzler.h b/src/codec/SkSwizzler.h
index bdb10a14163da8b14f58569f23638fa5b3db3eea..ee449aed7cc252825112060d4bab8d0828566a15 100644
--- a/src/codec/SkSwizzler.h
+++ b/src/codec/SkSwizzler.h
@@ -192,6 +192,12 @@ private:
                                    int dstWidth, int bpp, int deltaSrc, int offset,
                                    const SkPMColor ctable[]);
 
+    template <RowProc proc>
+    static ResultAlpha SkipLeading8888ZerosThen(void* SK_RESTRICT dstRow,
+                                                const uint8_t* SK_RESTRICT src,
+                                                int dstWidth, int bpp, int deltaSrc, int offset,
+                                                const SkPMColor ctable[]);
+
     const RowProc       fRowProc;
     const SkPMColor*    fColorTable;      // Unowned pointer