Risky borrowers are running into trouble in China and that is putting pressure on trust companies, an important corner of the country’s shadow-banking system. The fear is that this could further reduce the credit available for private businesses, acting as a drag on an economy whose growth is already slowing. Lightly regulated trust companies have been critical lenders for these firms, as traditional banks deal mostly with favored state-owned enterprises. These problems could also bounce back on many small investors. …