Frost cut it to 3-1 at 6:47 of the third period. Travis Konecny's shot was tipped wide of the net, and Frost scored on a carom off the boards.
That was the only mistake DeSmith made in his first start since Dec. 31.
"What a great luxury to have, when you can rest Jake [Oettinger] and you know you're going to get a performance like that," DeBoer said.
It was DeSmith's third start since Dec. 2, but Dallas has 11 games in 21 days starting against the Montreal Canadiens on Saturday, so he likely will start to see more action.
"I have a good amount of confidence going right now, and the team is making it easy on me," DeSmith said. "We played great tonight I thought in every end of the ice. We really dictated play. We played our game and played offensively without selling the farm for offense, and we're just doing a great job of finding that balance, night in, night out."
Heiskanen closed the scoring with an empty-net goal at 16:47. It was the defenseman's first goal since Nov. 25.
"I thought for the last stretch of games, even thought we haven't been winning or getting points, I felt we've been playing pretty good," Frost said. "Good enough to get a point out of a game or win the game. Tonight wasn't the same. Just lacked energy throughout the game and couldn't string plays together. Just got to refresh the mind and come back next game and hopefully we can go on a streak here."
NOTES: The Stars' winning streak is their longest since going eight straight from March 16-April 3 last season. Their road winning streak is their longest since a seven-game run March 5-30 last season. ... Stars captain Jamie Benn had an assist on Johnston's goal to give him four points (three goals, one assist) during a four-game point streak. ... Dumba had gone 10 games without a point before his assist on Bourque's goal, and was back in the lineup after being scratched Tuesday. ... Johnston now has 30 points (10 goals, 20 assists). He joined Benn (15) and John Klingberg (eight) as the only Stars players in the past 15 years to have at least 30 points in each of his first three NHL seasons. ... Dallas' 26 wins is tied for its second-most through 40 games of a season (also 2005-06 and 1998-99), behind the 28 wins it had after 40 games in 2015-16. ... Flyers forward Noah Cates had his four-game point streak (four assists) end.