Merge to M47: Fix extraction of colour components in CPDF_DIBSource::DownSampleScanline32Bit

Previously, if |m_bpc| was < 8 (e.g. 4), this function may still try to
access the source components as if |m_bpc| == 8. Even when it fell into
the codepath that tried to do the right thing in this case, it was
wrong.

BUG=554151

Review URL: https://codereview.chromium.org/1433423002 .

(cherry picked from commit e21fe98d5b5da7da01503b985b07b90c8e811689)

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1441973002 .
1 file changed