Non DCTSIZE multiple width support for JPEG YUV decoding

Since jpeg_read_raw_data reads blocks of memory, we have to make sure
that the memory allocated is a multiple of the DCT block size. For
example, if DCTSIZE is 8, which is generally the case, we have to make
sure that the allocated memory to read the raw JPEG data has a width
rounded up to the next multiple of 8 (if it's not already a multiple
of 8) to avoid writing data out of the bounds of the memory. If this
isn't done properly, the end of some decode image lines can overwrite
the beginning of the following lines.

BUG=411189

Review URL: https://codereview.chromium.org/544323002

git-svn-id: svn://svn.chromium.org/blink/trunk@181749 bbb929c8-8fbe-4397-9dbb-9b2b20218538