Currently, only the grid container needs the containing block size to resolve
the transferred min and max sizes for `repeat()` function in
`nsGridContainerFrame::ComputeIntrinsicISize()`.
This patch is a preparation for Bug 1865438. `mContainingBlockSize` will be used
there, so it does not change any behavior yet.
Differential Revision: https://phabricator.services.mozilla.com/D221333