Yes, it was removed from AOSP due to bit rot. It wasn't accidentally omitted.
-bri
~/aosp-master/.repo/manifests$ git log -S packages/inputmethods/PinyinIME
commit 184c029d911e7da159f3dbfb898099686b10eaa0
Author: Bill Yi <
b...@google.com>
Date: Fri May 15 09:07:13 2015 -0700
Remove base gpl files
Change-Id: I6b3e3cd4270965e57e4d41e92128adb6927e88cd
commit 276fcd8bd6e08baa07e71a0e51af2a7173960bf8
Author: Bill Yi <b...@google.com>
Date: Fri Sep 19 12:03:56 2014 -0700
Remove packages/inputmethods/PinyinIME
BUG:17578207
Change-Id: Ifc2a3990312ecfc4cb3dae4a7037938ab187946b
...