Increase buffer size for XMPP sockets.

Increase buffer size for XMPP sockets.

Previously 4096 bytes write buffer was used for XMPP socket. Problem is
that ChromeAsyncSocket stops writing when the buffer is full and
talk::XmppClient ignores this error, as result random chunks of data may
be lost. This CL increses buffer size to 64k - same value that's used in
notifier::XmppConnection.
This is essentially a temporary workaround until the problem is fixed
in jingle::ChromeAsyncSocket or talk::XmppClient

BUG=417336
Committed: https://crrev.com/4f18b99844271e085918cdcfab318ecede81f135
Cr-Commit-Position: refs/heads/master@{#296805}

[Sergey Ulanov, 2014-09-25 19:10:06]

sergeyu@chromium.org changed reviewers:
+ rmsousa@chromium.org

[rmsousa, 2014-09-25 20:22:19]

lgtm

Lgtm

[Sergey Ulanov, 2014-09-25 20:35:24]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2014-09-25 20:36:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/608613002/1

[commit-bot: I haz the power, 2014-09-25 22:09:17]

Committed patchset #1 (id:1) as 1e9218e387859e3bb0ebefa101f205b2acf81f80

[commit-bot: I haz the power, 2014-09-25 22:11:22]

Patchset 1 (id:??) landed as
https://crrev.com/4f18b99844271e085918cdcfab318ecede81f135
Cr-Commit-Position: refs/heads/master@{#296805}