SkCodec: add wbmp class

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 117 matching lines @@
      *      those of getInfo, this implies a scale.
      *  @return New SkScanlineDecoder on success, NULL otherwise. The SkCodec
      *      will take ownership of the returned scanline decoder.
      */
     virtual SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo) {
         return NULL;
     }
 
     virtual bool onReallyHasAlpha() const { return false; }
 
+    enum RewindState {
+        kRewound_RewindState,
+        kNoRewindNecessary_RewindState,
+        kCouldNotRewind_RewindState
+    };
     /**
      *  If the stream was previously read, attempt to rewind.
      *  @returns:
-     *      true
-     *       - if the stream needed to be rewound, and the rewind
-     *         succeeded.
-     *       - if the stream did not need to be rewound.
-     *      false
-     *       - if the stream needed to be rewound, and rewind failed.
+     *      kRewound if the stream needed to be rewound, and the
+     *               rewind succeeded.
+     *      kNoRewindNecessary if the stream did not need to be
+     *                         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.
      */
-    bool SK_WARN_UNUSED_RESULT rewindIfNeeded();
+    RewindState SK_WARN_UNUSED_RESULT rewindIfNeeded();
 
     /*
      *
      * Get method for the input stream
      *
      */
     SkStream* stream() {
         return fStream.get();
     }
 
 private:
 #ifdef SK_SUPPORT_LEGACY_BOOL_ONGETINFO
     const SkImageInfo                   fInfo;
 #endif  //  SK_SUPPORT_LEGACY_BOOL_ONGETINFO
     SkAutoTDelete<SkStream>             fStream;
     bool                                fNeedsRewind;
     SkAutoTDelete<SkScanlineDecoder>    fScanlineDecoder;
 
     typedef SkImageGenerator INHERITED;
 };
 #endif // SkCodec_DEFINED