Mojo: Don't do any work in ProxyMessagePipeEndpoint's destructor.

Mojo: Don't do any work in ProxyMessagePipeEndpoint's destructor.

In particular, detach from the ChannelEndpoint earlier.

(The ChannelEndpoint has a pointer to the MessagePipe that owns the
ProxyMessagePipeEndpoint. It should always be valid. Detaching in the
ProxyMessagePipeEndpoint's destructor means that that pointer is
momentarily not really valid -- "not really" in that the memory still
exists, but it's in the middle of the MessagePipe's destruction.)

R=brettw@chromium.org

Committed: https://crrev.com/15235c63c9a50d40d31f766bd968feaa8c298876
Cr-Commit-Position: refs/heads/master@{#297673}

[brettw, 2014-10-01 17:40:41]

lgtm

[viettrungluu, 2014-10-01 17:44:22]

The CQ bit was checked by viettrungluu@chromium.org

[commit-bot: I haz the power, 2014-10-01 17:46:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/619623003/1

[commit-bot: I haz the power, 2014-10-01 17:51:08]

Committed patchset #1 (id:1) as ebfb4ff0370c7dcd7018d7d84ed8641f5c2ca58f

[commit-bot: I haz the power, 2014-10-01 17:51:39]

Patchset 1 (id:??) landed as
https://crrev.com/15235c63c9a50d40d31f766bd968feaa8c298876
Cr-Commit-Position: refs/heads/master@{#297673}