While Siri’s debut on Mac, Apple‘s (NASDAQ: AAPL) decision to hand over the voice assistant to iOS app developers, and instant apps for Apple Watch may have stolen the show at Apple’s Worldwide Developers Conference, or WWDC, there’s another takeaway from the event that Facebook (NASDAQ: FB) investors may want to hone in on: Apple heavily endorsed Facebook’s big bet on messaging and launched major features to integrate third-party message apps like Facebook’s Messenger and Whatsapp prominently in iOS.