Remove associated interface registration from ChannelProxy

ChannelProxy already delegates incoming associated interface requests
to its Listener if they weren't handled by the Channel.

We use this instead of having ChannelProxy register UI-thread-posting
binders on the Channel itself. It's simpler and safer this way.

BUG=683773
R=jam@chromium.org

Review-Url: https://codereview.chromium.org/2653973002
Cr-Commit-Position: refs/heads/master@{#445886}
11 files changed