SAN RAMON, Calif. (AP) — On Monday, Apple faces a trial that could upend its iron control over its app store, which brings in billions of dollars each year while feeding more than 1.6 billion iPhones, iPads, and other devices. The case, which represents one of Apple’s most serious legal threats in recent years, comes from Epic Games, maker of the popular video game Fortnite. Epic charges that Apple has transformed its once-tiny digital storefront into an illegal monopoly that squeezes mobile apps for a slice of their earnings. Apple denies that charge and seeks to depict Epic as a would-be freeloader on its app store.