Switch LayoutLib to Java 8

The main build hasn't swtiched to java 8, but lambdas are already used
in layoutlib. This fixes the build break.

(cherry picked from commit 7914e4ca03322427740d6f8c00837375dbf3031a)

Change-Id: Ice5741dcb8b93faf739a3c21f2ed8be95f92ad08
5 files changed