Individually enable and disable SkCodecs

src/codec/SkJpegCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkJpegCodec_DEFINED
 #define SkJpegCodec_DEFINED
 
 #include "SkCodec.h"
 #include "SkImageInfo.h"
-#include "SkJpegDecoderMgr.h"
-#include "SkJpegUtility_codec.h"
+#include "SkSwizzler.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
 
-extern "C" {
-    #include "jpeglib.h"
-}
+class JpegDecoderMgr;
 
 /*
  *
  * This class implements the decoding for jpeg images
  *
  */
 class SkJpegCodec : public SkCodec {
 public:
     static bool IsJpeg(const void*, size_t);
 
@@ skipping 86 matching lines @@
 
     // scanline decoding
     SkAutoTMalloc<uint8_t>     fStorage;    // Only used if sampling is needed
     uint8_t*                   fSrcRow;     // Only used if sampling is needed
     SkAutoTDelete<SkSwizzler>  fSwizzler;
     
     typedef SkCodec INHERITED;
 };
 
 #endif