When both luma and chroma are copied to the local buffer (either
due to yuv format conversion, or due to padding), they have got
the same stride, but if chroma is copied while luma is used directly
from the input buffer, they might have different strides.
Therefore add a separate field for chroma stride.
This commit only adds the field, while it still has got the same
value as before.
Change-Id: I0dce97ad4d91cd1d9aba4b4472c6a0de45a314bc
9113f5615c