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 90099f057e80a90d96969ece303e56b48064c59f..f23296f85895be48e4a772c85504d775fa929121 100644
--- a/src/codec/SkSwizzler.h
+++ b/src/codec/SkSwizzler.h
@@ -154,6 +154,12 @@ private:
                             int dstWidth, int bpp, int deltaSrc, int offset,
                             const SkPMColor ctable[]);
 
+    template <RowProc Proc>
+    static void 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