Gardening: Fix build with AddressSanitizer.
Remove un-necessary OnChannelClosed function.

DisplayChannelHost is already notified when channel is closed via
OnChannelClosing(IPC::ChannelProxy::MessageFilter). OnChannelClosed
is un-necessary, thus removing its usage.
Remove InputMethodEventFilter

Aura registers a views::corewm::InputMethodEventFilter as an
event filter, and the InputMethodEventFilter uses an implementation
of ui::InputMethod. Ozone implementations should provide any custom
implementation by extending InputMethodContext(will do in a followup
patch) and not InputMethodEventFilter. This patch removes
WaylandInputMethodEventFilter.