Issue #195104 in the AOSP Issue Tracker was created back on November 24th, 2015. The bug report details a memory leak that pertains to the System UI for Android and for months the Android team has been trying to pinpoint the problem. While one comment from March says the memory leak was fixed with build MMB29V, a Google project member replied to the thread today and said the issue was now fixed. They said the bug fix for this memory leak would be included in a future release. They don't say which future release, but it's believed that it will be included in the July security update.