am c6ff6c40: Merge "gralloc: Clarify alloc stride for HAL_PIXEL_FORMAT_YCbCr_420_888" into jb-mr2-dev

* commit 'c6ff6c40dd4408c7aac0e079a6d26359902c240f':
  gralloc: Clarify alloc stride for HAL_PIXEL_FORMAT_YCbCr_420_888