Implement parenthesis-handling fixes for Sass in Vaadin 7.1 (#12834)

These are the same changes that were done for the master-branch in
(#12833).

Change-Id: I397028c7b0ba06567adaad9f0f0095157f7ae8f9
Merge: no
No-op merge from origin/7.1

b008768 Implement parenthesis-handling fixes for Sass in Vaadin 7.1 (#12834)

Change-Id: Iaa13fd76a784ba20216e200157740cf55a76054a
Merge "No-op merge from origin/7.1"