Yes, I believe that countries benefit economically from population growth, because there are more people in the country to work and be productive. Even though China isn't really economically all that strong, they are a power with a lot of market interest, simply because they have a large population. New workers can invent new things.
In order for a country to grow economically, they need people. Population growth is extremely helpful in economical growth. A country can not expect to see their economical status change for the better if people are constantly leaving the country. They need more people to enter the area to help it grow.
Seems like an easy enough solution set, at least until you outstrip the jobs available, everything is a balance. Taking in a few million refugee's from a failed state next door might cause a bit of a glut in the labor market, but over time, it's grow or die, and always has been, there is no standing still in nature.
Perhaps the opposite because when countries have a population growth (boom) than they are more likely to have to spend more money to help the influx of people who are growing and living in that country and the government must in turn spend more money to support the influx of people in that country.
I think there was a time and place where they did grow from population influxes,but times are very different now. I think the less the better. Social programs are maxed out and the less the government has to help the better. I think Japan is about max, they even build land to help the issue.