Add logging to CHECK failure during curtain-mode on Mac.

Add logging to CHECK failure during curtain-mode on Mac.

BUG=446327
Committed: https://crrev.com/c013db41d32c5da4e88a173ad03eadcab33bf974
Cr-Commit-Position: refs/heads/master@{#322098}

[Lambros, 2015-03-24 18:48:02]

lambroslambrou@chromium.org changed reviewers:
+ jamiewalch@chromium.org

[Jamie, 2015-03-24 19:24:47]

lgtm

https://codereview.chromium.org/1026553005/diff/1/remoting/host/curtain_mode_...
File remoting/host/curtain_mode_mac.cc (right):

https://codereview.chromium.org/1026553005/diff/1/remoting/host/curtain_mode_...
remoting/host/curtain_mode_mac.cc:149: << "CGSessionCopyCurrentDictionary()
returned NULL.";
Can you add a message to the effect that logging out will probably resolve the
problem?

[Lambros, 2015-03-24 23:07:36]

The CQ bit was checked by lambroslambrou@chromium.org

[Lambros, 2015-03-24 23:07:37]

The patchset sent to the CQ was uploaded after l-g-t-m from
jamiewalch@chromium.org
Link to the patchset: https://codereview.chromium.org/1026553005/#ps20001
(title: "Log more info.")

[commit-bot: I haz the power, 2015-03-24 23:08:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1026553005/20001

[commit-bot: I haz the power, 2015-03-25 00:01:35]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-25 00:02:27]

Patchset 2 (id:??) landed as
https://crrev.com/c013db41d32c5da4e88a173ad03eadcab33bf974
Cr-Commit-Position: refs/heads/master@{#322098}