refactor(material/snack-bar): refactor variable type to const in snack-bar component unit tests (#22774)
refactor(material/snack-bar): refactor variable type to const in snack-bar component unit tests (#22774)

style(material/snack-bar): fix tslint trailing whitespace issue in ci build
DevVersion/material2,crisbeto/material2,josephperrott/material2,angular/components,angular/components,crisbeto/material2,crisbeto/material2,mmalerba/material2,josephperrott/material2,angular/components,mmalerba/material2,josephperrott/material2,angular/components,mmalerba/material2,josephperrott/material2,DevVersion/material2,josephperrott/material2,mmalerba/material2,DevVersion/material2,DevVersion/material2,crisbeto/material2,mmalerba/material2,DevVersion/material2