Call rewindIfNeeded in SkCodec

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 384 matching lines @@
 
     virtual bool onReallyHasAlpha() const { return false; }
 
     /**
      *  If the stream was previously read, attempt to rewind.
      *
      *  If the stream needed to be rewound, call onRewind.
      *  @returns true if the codec is at the right position and can be used.
      *      false if there was a failure to rewind.
      *
-     *  Subclasses MUST call this function before reading the stream (e.g. in
-     *  onGetPixels). If it returns false, onGetPixels should return
-     *  kCouldNotRewind.
+     *  This is called by getPixels() and start(). Subclasses may call if they
+     *  need to rewind at another time.
      */
     bool SK_WARN_UNUSED_RESULT rewindIfNeeded();
 
     /**
      *  Called by rewindIfNeeded, if the stream needed to be rewound.
      *
      *  Subclasses should do any set up needed after a rewind.
      */
     virtual bool onRewind() {
         return true;
@@ skipping 55 matching lines @@
         return this->onGetScanlines(storage.get(), countLines, 0);
     }
 
     virtual SkCodec::Result onGetScanlines(void* dst, int countLines,
                                                     size_t rowBytes) {
         return kUnimplemented;
     }
 
 };
 #endif // SkCodec_DEFINED