Destroy SkScanlineDecoder in the SkCodec subclass destructors

include/codec/SkCodec.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 SkCodec_DEFINED
 #define SkCodec_DEFINED
 
@@ skipping 150 matching lines @@
      *                         rewound.
      *      kCouldNotRewind if the stream needed to be rewound, and
      *                      rewind failed.
      *
      *  Subclasses MUST call this function before reading the stream (e.g. in
      *  onGetPixels). If it returns false, onGetPixels should return
      *  kCouldNotRewind.
      */
     RewindState SK_WARN_UNUSED_RESULT rewindIfNeeded();
 
-    /*
-     *
+    /**
      * Get method for the input stream
-     *
      */
     SkStream* stream() {
         return fStream.get();
     }
 
+    /**
+     * If the codec has a scanline decoder, return it (no ownership change occurs)
+     * else return NULL.
+     * The returned decoder is valid while the codec exists and the client has not
+     * created a new scanline decoder.
+     */
+    SkScanlineDecoder* scanlineDecoder() {
+        return fScanlineDecoder.get();
+    }
+
+    /**
+     * Allow the codec subclass to detach and take ownership of the scanline decoder.
+     * This will likely be used when the scanline decoder needs to be destroyed
+     * in the destructor of the subclass.
+     */
+    SkScanlineDecoder* detachScanlineDecoder() {
+        return fScanlineDecoder.detach();
+    }
+
 private:
     SkAutoTDelete<SkStream>             fStream;
     bool                                fNeedsRewind;
     SkAutoTDelete<SkScanlineDecoder>    fScanlineDecoder;
 
     typedef SkImageGenerator INHERITED;
 };
 #endif // SkCodec_DEFINED