Merge 102519 - WebPImageDecoder progressive decodes fail to decode valid images

Merge 102519 - WebPImageDecoder progressive decodes fail to decode valid images
https://bugs.webkit.org/show_bug.cgi?id=74062

Reviewed by Adam Barth.

The WEBP header is followed by a so-called P0 header, then some data to
decode.  If a partial P0 header is received during progressive decodes,
WebPIDecGetRGB() returns false; that makes the decoder enter the failed
state, no image appears on the page.

James Zern (webp) recommended the following via e-mail:

WebPIUpdate() validates input data, and will return an error status for
malformed data (bit-stream error, invalid data).  Otherwise, it returns
OK or SUSPENDED.  OK means that decoding is done/complete/no-error, and
SUSPENDED means more input data is needed to complete decoding.  A NULL
return from WebPIDecGetRGB() is valid at this time due to a partial P0,
and should not be interpreted as a decoding failure.

No new tests. Not something DumpRenderTree can easily test.

* platform/image-decoders/webp/WEBPImageDecoder.cpp:
(WebCore::WEBPImageDecoder::decode):  A NULL WebPIDecGetRGB() return is
acceptable here.  Return false instead of failing the decoder.


TBR=noel.gordon@gmail.com
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=103269

[Noel Gordon, 2011-12-20 00:55:38]

LGTM.