Handle rewinds in SkBmpCodec.

src/codec/SkCodec_libbmp.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.
  */
 
 #include "SkCodec.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
@@ skipping 82 matching lines @@
     /*
      *
      * Creates a bmp decoder
      * Reads enough of the stream to determine the image format
      *
      */
     static SkCodec* NewFromStream(SkStream*, bool isIco);
 
     /*
      *
+     * Read enough of the stream to initialize the SkBmpCodec. Returns a bool
+     * representing success or failure. If it returned true, and codecOut was
+     * not NULL, it will be set to a new SkBmpCodec.
+     *
+     */
+    static bool ReadHeader(SkStream*, bool isIco, SkCodec** codecOut);
+
+    /*
+     *
      * Performs the bitmap decoding for bit masks input format
      *
      */
     Result decodeMask(const SkImageInfo& dstInfo, void* dst,
                       size_t dstRowBytes);
 
     /*
      *
      * Set an RLE pixel using the color table
      *
@@ skipping 61 matching lines @@
     SkAutoTDelete<SkColorTable>         fColorTable;     // owned
     uint32_t                            fNumColors;
     const uint32_t                      fBytesPerColor;
     const uint32_t                      fOffset;
     const RowOrder                      fRowOrder;
     const size_t                        fRLEBytes;
     const bool                          fIsIco;
 
     typedef SkCodec INHERITED;
 };