The flow of foreign labor into the United Arab Emirates is drying up, leaving the country's leaders to grapple with a tricky balancing act: How to attract and retain enough workers from abroad to keep its economy humming without alienating its own citizens. As it looks to bolster its labor market, Abu Dhabi has instituted a range of stimulus plans, visa reforms and business law changes over the past year. But those solutions risk upsetting Emirati natives, who see extended-stay expatriates as a threat to their way of life and elevated social status. Their discomfort opens the door for a historic shift in the country's generally stable political system....