Update docs for InterfacePtr and Binding. Bug: None Change-Id: I476e1ba191391085cc6719b07c90fa0a6f2e42db Reviewed-on: https://chromium-review.googlesource.com/775676 Reviewed-by: James Cook <[email protected]> Cr-Commit-Position: refs/heads/master@{#517210} CrOS-Libchrome-Original-Commit: 7afd726d1b885828893ffd3aabfaad0fb2cde63c