Handle SkStream::rewind properly.

src/images/SkImageDecoder_libpng.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkImageDecoder.h"
@@ skipping 106 matching lines @@
     SkStream* sk_stream = (SkStream*) png_get_io_ptr(png_ptr);
     size_t bytes = sk_stream->read(data, length);
     if (bytes != length) {
         png_error(png_ptr, "Read Error!");
     }
 }
 
 #ifdef SK_BUILD_FOR_ANDROID
 static void sk_seek_fn(png_structp png_ptr, png_uint_32 offset) {
     SkStream* sk_stream = (SkStream*) png_get_io_ptr(png_ptr);
-    sk_stream->rewind();
+    if (!sk_stream->rewind()) {
+        png_error(png_ptr, "Failed to rewind stream!");
+    }
     (void)sk_stream->skip(offset);
 }
 #endif
 
 static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
     SkImageDecoder::Peeker* peeker =
                     (SkImageDecoder::Peeker*)png_get_user_chunk_ptr(png_ptr);
     // peek() returning true means continue decoding
     return peeker->peek((const char*)chunk->name, chunk->data, chunk->size) ?
             1 : -1;
@@ skipping 1059 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? SkNEW(SkPNGImageEncoder) : NULL;
 }
 
 static SkTRegistry<SkImageEncoder*, SkImageEncoder::Type> gEReg(sk_libpng_efactory);
 static SkTRegistry<SkImageDecoder::Format, SkStream*> gFormatReg(get_format_png);
 static SkTRegistry<SkImageDecoder*, SkStream*> gDReg(sk_libpng_dfactory);