When I first got my Nexus 5 I switched to ART from Dalvik and everything was fine. I then rooted it and after a while of it being rooted I decided to revert to stock, so I factory reset my phone but now even though it's no longer rooted when I try to switch to ART it reboots yet the phone remains in Dalvik anyways. What's wrong and how do I fix this? I've heard that Xblast Tools is the culprit but I honestly don't know.