Don't use NEON optimized code in lpng_v163

samples/fx_lpng/lpng_v163/pngpriv.h

Index: samples/fx_lpng/lpng_v163/pngpriv.h
diff --git a/samples/fx_lpng/lpng_v163/pngpriv.h b/samples/fx_lpng/lpng_v163/pngpriv.h
index 7fa3d6059cd6151a9ca25c9c2c6d724ab41fc908..18965380c86eb9c18c5a0c8e1b698e9063b8ae05 100644
--- a/samples/fx_lpng/lpng_v163/pngpriv.h
+++ b/samples/fx_lpng/lpng_v163/pngpriv.h
@@ -107,6 +107,11 @@
  * this in $(CC), e.g. "CC=gcc -mfpu=neon", but people who build libpng rarely
  * do this.
  */
+/*
+ * pdfium: This version of libpng does not contain the arm neon optimized code
+ * so we should never try to reference it.
+ */
+#if 0
 #ifndef PNG_ARM_NEON_OPT
    /* ARM NEON optimizations are being controlled by the compiler settings,
     * typically the target FPU.  If the FPU has been set to NEON (-mfpu=neon
@@ -127,6 +132,7 @@
     */
 #  define PNG_FILTER_OPTIMIZATIONS png_init_filter_functions_neon
 #endif
+#endif
 
 /* Is this a build of a DLL where compilation of the object modules requires
  * different preprocessor settings to those required for a simple library?  If