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_ktx.cpp b/src/images/SkImageDecoder_ktx.cpp
index fd1db5e..effc1ed 100644
--- a/src/images/SkImageDecoder_ktx.cpp
+++ b/src/images/SkImageDecoder_ktx.cpp
@@ -62,10 +62,12 @@
     const unsigned short width = ktxFile.width();
     const unsigned short height = ktxFile.height();
 
+#ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
     // should we allow the Chooser (if present) to pick a config for us???
     if (!this->chooseFromOneChoice(kN32_SkColorType, width, height)) {
         return false;
     }
+#endif
 
     // Set a flag if our source is premultiplied alpha
     const SkString premulKey("KTXPremultipliedAlpha");