Another feature added to the YouTube app gives users the opportunity to view their handiwork with an inline preview before pressing the "upload now" button. This makes sure that the video is exactly as they want it (including the trimming) before it is too late to make any changes.
Google is said to be working on other new things for YouTube to offer budding young directors such as Instagram styled filters, and licensed music to replace their audio. But those are for future updates. Today is all about the trim.