Add optimize_coding setting for JPEG encoding.

src/images/SkImageDecoder_libjpeg.cpp

Index: src/images/SkImageDecoder_libjpeg.cpp
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index 0d02a658f29626acef03df8b523de9bdce9f8fee..6a032fdb9626703ffe3d8a669b497759339d6bd0 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -958,6 +958,7 @@ protected:
         cinfo.input_gamma = 1;
 
         jpeg_set_defaults(&cinfo);
+        cinfo.optimize_coding = TRUE;
         jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
 #ifdef DCT_IFAST_SUPPORTED
         cinfo.dct_method = JDCT_IFAST;