Delete some unused code found by -Wunused-function

ui/gfx/codec/jpeg_codec.cc

Index: ui/gfx/codec/jpeg_codec.cc
diff --git a/ui/gfx/codec/jpeg_codec.cc b/ui/gfx/codec/jpeg_codec.cc
index bfa47b97d5537cfff2246b34239fe14054478c62..1cfd68dbbab2103d8e6f3e5da45f2802bdf9b0f9 100644
--- a/ui/gfx/codec/jpeg_codec.cc
+++ b/ui/gfx/codec/jpeg_codec.cc
@@ -143,6 +143,7 @@ void TermDestination(jpeg_compress_struct* cinfo) {
   state->out->resize(state->image_buffer_used);
 }
 
+#if !defined(JCS_EXTENSIONS)
 // Converts RGBA to RGB (removing the alpha values) to prepare to send data to
 // libjpeg. This converts one row of data in rgba with the given width in
 // pixels the the given rgb destination buffer (which should have enough space
@@ -172,6 +173,7 @@ void BGRAtoRGB(const unsigned char* bgra, int pixel_width, unsigned char* rgb)
     pixel_out[2] = pixel_in[0];
   }
 }
+#endif  // !defined(JCS_EXTENSIONS)
 
 // This class destroys the given jpeg_compress object when it goes out of
 // scope. It simplifies the error handling in Encode (and even applies to the
@@ -393,6 +395,7 @@ void SkipInputData(j_decompress_ptr cinfo, long num_bytes) {
 void TermSource(j_decompress_ptr cinfo) {
 }
 
+#if !defined(JCS_EXTENSIONS)
 // Converts one row of rgb data to rgba data by adding a fully-opaque alpha
 // value.
 void AddAlpha(const unsigned char* rgb, int pixel_width, unsigned char* rgba) {
@@ -419,6 +422,7 @@ void RGBtoBGRA(const unsigned char* bgra, int pixel_width, unsigned char* rgb)
     pixel_out[3] = 0xff;
   }
 }
+#endif  // !defined(JCS_EXTENSIONS)
 
 // This class destroys the given jpeg_decompress object when it goes out of
 // scope. It simplifies the error handling in Decode (and even applies to the