Remove duplicate entries in methods to diff and predicates to test

This patch ensures that in the case where a method/predicate depends on
multiple properties in a generated group the function only appears in
the generator once.

Diff: https://gist.github.com/nainar/c4d5c74597627e5dcde5f6caad377391/revisions

BUG=710938

Review-Url: https://codereview.chromium.org/2940613003
Cr-Commit-Position: refs/heads/master@{#479320}
1 file changed