Merge to M47: Clear decoders after the image decoder in the /Filter array.

During decoding, when an image decoder is encountered, any
subsequent decoders are ignored, but remain in the array. However,
later on CPDF_DIBSource::ValidateDictParam expects the image
decoder to be the last in the array, causing issues.

A check is also added in CPDF_DIBSource::GetScanline to ensure
that the calculated pitch value is <= the (4-aligned) pitch value in the
cached bitmap to prevent future issues.

Also cleans up some NULL usages.

BUG=552046

Review URL: https://codereview.chromium.org/1406943005 .

(cherry picked from commit 182d129bcee8f7731b9bbfde0064295ad3b37271)

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1444503002 .
4 files changed