Merge "Expand javadoc for Build.VERSION.KNOWN_CODENAMES." am: 4ff7b1d723 am: f8e89c239f

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1979486

Change-Id: I6617ac35d6946ed4f1884ba7a6f8c832f96cd4e5