Bug 983991 - Ensure the pagination bar layer is always here. r=crdlc
Bug 983991 - Move the will-change rule from ol to .page. r=crdlc
Bug 983991 - Do not reflows on panels changes. r=crdlc
Bug 983991 - Keep panels partly on screen after transition to preserve their layers. r=crdlc
Merge pull request #17248 from vingtetun/bug983991.keep.layers

Bug983991.keep.layers