mus: Make sure WindowCompositorFrameSink is detached correctly.

WindowCompositorFrameSink is detached from the client on the same thread
it is attached to the client, which can be different from the thread it
is created/destroyed on. So, all the thread-hostile objects created
during attachment (i.e. in BindToClient()) needs to be destroyed during
detach (i.e. in DetachFromClient()), because otherwise they will be
destroyed during the destruction of a WindowCompositorFrameSink on a
different thread, causing crashes etc. |client_binding_| is such a
thread-hostile object, so make sure it is destroyed during detach.


Cr-Commit-Position: refs/heads/master@{#445761}
1 file changed