The Android Open Source Project is a great tool for developers and generally interested persons who simply want to take a look around the newest versions of the code that Google drops, and it seems the latest version of the code listed as build number LMY47V has just been uploaded to AOSP. This is listed as Android 5.1.1, which reportedly fixes and issue with the memory leak that has been plaguing Nexus devices since Lollipop was released. Not too long ago Google had mentioned they were looking into the memory leak problem and eventually that they had found a fix for it internally, but at the time they mentioned they didn't have a time frame for when the fix would be made public. It would appear that this new update may include the fix for the issue that has persisted on user device through the different versions of Lollipop.
With the recent new factory image for the Nexus Player going out earlier this morning, we may end up seeing software updates and factory images drops for the remaining supported Nexus devices in the near future and likely a few weeks out. Right now we don't have any details about what is all included with the new software version, but rest assured as soon as the full changelog becomes available the details will be posted.
For now, the source code being uploaded is really only useful for developers who will be using the source code to work with for development, fixes, improvements etc. for their applications, custom firmware and other software pertaining to specific parts of the Android software and devices. As such, the source code might not mean much to the average user, as it's the details of what has changed that may be of interest since it could positively affect the user experience of the device going forward. The memory leak issue is probably not the only fix that users can expect when the software begins pushing out to devices, which should make some users happy if they have been having more than the memory leak issue. If you want to download the source code you can access it from the source link below.