Handle SkStream::rewind properly.

src/images/SkImageDecoder_libwebp.cpp

Index: src/images/SkImageDecoder_libwebp.cpp
diff --git a/src/images/SkImageDecoder_libwebp.cpp b/src/images/SkImageDecoder_libwebp.cpp
index 9f1116e5d5bbbd51c8e168f12d8db99d585f07f6..ef2ee6aa62a8db0c018a55e528cd79fdbf08afa9 100644
--- a/src/images/SkImageDecoder_libwebp.cpp
+++ b/src/images/SkImageDecoder_libwebp.cpp
@@ -199,7 +199,10 @@ static bool webp_idecode(SkStream* stream, WebPDecoderConfig* config) {
         return false;
     }
 
-    stream->rewind();
+    if (!stream->rewind()) {
+        SkDEBUGF(("Failed to rewind webp stream!"));

[djsollen, 2013/08/22 19:59:18]

should we always print this?

[scroggo, 2013/08/23 21:14:07]

Any reason not to? This will tell the caller that they failed due to problems
rewinding the stream, rather than bad data, for example.

[djsollen, 2013/08/25 17:47:19]

I agree that we should print this always.   That is why I would use SkDebugf
instead of the debug only SkDEBUGF.

[scroggo, 2013/08/26 16:37:47]

Ah, now I understand your comment. I didn't know the difference between SkDebugf
and SkDEBUGF. I used SkDEBUGF because it was used by
SkImageDecoder_FactoryRegistrar.

Done.

+        return false;
+    }
     const size_t readBufferSize = stream->hasLength() ?
             SkTMin(stream->getLength(), WEBP_IDECODE_BUFFER_SZ) : WEBP_IDECODE_BUFFER_SZ;
     SkAutoMalloc srcStorage(readBufferSize);
@@ -311,7 +314,11 @@ bool SkWEBPImageDecoder::onBuildTileIndex(SkStream* stream,
         return false;
     }
 
-    stream->rewind();
+    if (!stream->rewind()) {
+        SkDEBUGF(("Failed to rewind webp stream!"));
+        return false;
+    }
+
     *width = origWidth;
     *height = origHeight;