hide SkImageDecoder::Chooser

BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/331433003
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index befe6dc..9b93716 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -613,10 +613,12 @@
     }
     sampleSize = recompute_sampleSize(sampleSize, cinfo);
 
+#ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
     // should we allow the Chooser (if present) to pick a colortype for us???
     if (!this->chooseFromOneChoice(colorType, cinfo.output_width, cinfo.output_height)) {
         return return_false(cinfo, *bm, "chooseFromOneChoice");
     }
+#endif
 
     SkScaledBitmapSampler sampler(cinfo.output_width, cinfo.output_height, sampleSize);
     // Assume an A8 bitmap is not opaque to avoid the check of each