Adds getLayoutInflater() to return a cached value.

Bug 37156970

Many applications need to get the LayoutInflater used for
fragment View inflation. onGetLayoutInflater() can be heavy
weight, so a version that caches that last value is added.

Support Lib: I11d719d7416a5bb3b65f37a78e6ed96a69c32332
Test: I6aa0ecfe7136d133d15a597857f6cf6f3cf68fca

Change-Id: I686d5b39f7a046396fff124c33c22a73952ee5d7