Remove unneeded reference to SkRasterizer

    static SkPixelRef* refSkPixelRef(JNIEnv*, jobject bitmap);

    static SkRegion* getNativeRegion(JNIEnv*, jobject region);

    // Given the 'native' long held by the Rasterizer.java object, return a

    // ref to its SkRasterizer* (or NULL).

    static sk_sp<SkRasterizer> refNativeRasterizer(jlong rasterizerHandle);

    /*

     *  LegacyBitmapConfig is the old enum in Skia that matched the enum int values

     *  in Bitmap.Config. Skia no longer supports this config, but has replaced it