Add a ChannelEndpointClient abstraction.

Add a ChannelEndpointClient abstraction.

This is to allow ChannelEndpoint to call things other than MessagePipe
(and make ChannelEndpoint know only about "clients" and not message
pipes). Clients can receive messages (from ChannelEndpoint, thus from
Channel), and be told that they'll no longer receive messages.

This is needed to allow Channel to handle certain "transitions" (when
passing message pipes between processes) specially, without dumping code
into MessagePipe.

R=yzshen@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/f99da059ef2d4f565dcda272b7cd94628ccedf51

[yzshen1, 2014-11-18 00:28:17]

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel.h
File mojo/edk/system/channel.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel.h#ne...
mojo/edk/system/channel.h:204: // are tied to the "remote" side. When
|ChannelEndpoint::OnDisconnect()|
I think there isn't OnDisconnect anymore

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel_endp...
File mojo/edk/system/channel_endpoint_client.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel_endp...
mojo/edk/system/channel_endpoint_client.h:45: // to the |ChannelEndpoint| (and
vice versa). After this is called,
This comment seems to conflict the comment at line 30.

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe.cc
File mojo/edk/system/message_pipe.cc (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe...
mojo/edk/system/message_pipe.cc:262: // This is called |ChannelEndpoint| for the
|ProxyMessagePipeEndpoint| on
nit: called -> called by

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe.h
File mojo/edk/system/message_pipe.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe...
mojo/edk/system/message_pipe.h:114: virtual bool OnReadMessage(unsigned port,
nit: I think the current style guide prefers using "override" without "virtual",
and the same for the destructor.

[viettrungluu, 2014-11-18 00:47:30]

Thanks, PTAL.

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel.h
File mojo/edk/system/channel.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel.h#ne...
mojo/edk/system/channel.h:204: // are tied to the "remote" side. When
|ChannelEndpoint::OnDisconnect()|
On 2014/11/18 00:28:17, yzshen1 wrote:
> I think there isn't OnDisconnect anymore

Done.

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel_endp...
File mojo/edk/system/channel_endpoint_client.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/channel_endp...
mojo/edk/system/channel_endpoint_client.h:45: // to the |ChannelEndpoint| (and
vice versa). After this is called,
On 2014/11/18 00:28:17, yzshen1 wrote:
> This comment seems to conflict the comment at line 30.

No it isn't.

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe.cc
File mojo/edk/system/message_pipe.cc (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe...
mojo/edk/system/message_pipe.cc:262: // This is called |ChannelEndpoint| for the
|ProxyMessagePipeEndpoint| on
On 2014/11/18 00:28:17, yzshen1 wrote:
> nit: called -> called by

"called when"

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe.h
File mojo/edk/system/message_pipe.h (right):

https://codereview.chromium.org/738453003/diff/1/mojo/edk/system/message_pipe...
mojo/edk/system/message_pipe.h:114: virtual bool OnReadMessage(unsigned port,
On 2014/11/18 00:28:17, yzshen1 wrote:
> nit: I think the current style guide prefers using "override" without
"virtual",
> and the same for the destructor.

Done.

[yzshen1, 2014-11-18 01:01:07]

lgtm

[viettrungluu, 2014-11-18 01:06:20]

Committed patchset #2 (id:20001) manually as
f99da059ef2d4f565dcda272b7cd94628ccedf51 (presubmit successful).