Fix PNG decoding divide by zero error due to zero row count.

Fix PNG decoding divide by zero error due to zero row count.

BUG=537790
R=tsepez@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/095a83c59120c108d9ac6f0ab71fd3faa5eea810

[Lei Zhang, 2015-10-02 02:05:32]

thestig@chromium.org changed reviewers:
+ tsepez@chromium.org

[Tom Sepez, 2015-10-02 16:44:25]

lgtm

https://codereview.chromium.org/1379243002/diff/1/core/src/fxcodec/codec/fx_c...
File core/src/fxcodec/codec/fx_codec_flate.cpp (right):

https://codereview.chromium.org/1379243002/diff/1/core/src/fxcodec/codec/fx_c...
core/src/fxcodec/codec/fx_codec_flate.cpp:403: if (row_count <= 0)
Yeah, ok, but this gets better using only unsigned types and safe types for
overflow handling. I'm sure there's some lurking grief if you can call this with
arbitrary arguments.

[Lei Zhang, 2015-10-02 17:27:48]

Committed patchset #1 (id:1) manually as
095a83c59120c108d9ac6f0ab71fd3faa5eea810 (presubmit successful).

[Lei Zhang, 2015-10-02 17:29:31]

https://codereview.chromium.org/1379243002/diff/1/core/src/fxcodec/codec/fx_c...
File core/src/fxcodec/codec/fx_codec_flate.cpp (right):

https://codereview.chromium.org/1379243002/diff/1/core/src/fxcodec/codec/fx_c...
core/src/fxcodec/codec/fx_codec_flate.cpp:403: if (row_count <= 0)
On 2015/10/02 16:44:25, Tom Sepez wrote:
> Yeah, ok, but this gets better using only unsigned types and safe types for
> overflow handling. I'm sure there's some lurking grief if you can call this
with
> arbitrary arguments.

Acknowledged.

[Lei Zhang, 2015-10-02 19:30:46]

Whoops, should have been BUG=537780.