Merge to XFA: Fix heap-buffer-overflow in color_sycc_to_rgb

It's a bug existing in the conversion from YUV420 to RGB.
For YUV 420 format, four pixels have 4 Y but only one U and
one V. In some cases, there are odd columns or lines in
some images. The pixels on last line or column may have Y
but no U or V data. For this case, We shall extend U or V
using the data on previous column or line.

BUG=497357
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1342683002 .
3 files changed