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

remoting/host/curtain_mode_mac.cc

Index: remoting/host/curtain_mode_mac.cc
diff --git a/remoting/host/curtain_mode_mac.cc b/remoting/host/curtain_mode_mac.cc
index cae8e704dfa1e202cc1380b841e2e830548603b6..fe4c483d1f0ce94aa6dfcc896a94342d7907143d 100644
--- a/remoting/host/curtain_mode_mac.cc
+++ b/remoting/host/curtain_mode_mac.cc
@@ -144,7 +144,9 @@ void SessionWatcher::ActivateCurtain() {
   // this, or how common it is, a crash report is useful in this case (note
   // that the connection would have to be refused in any case, so this is no
   // loss of functionality).
-  CHECK(session != nullptr);
+  CHECK(session != nullptr)
+      << "Error activating curtain-mode: "
+      << "CGSessionCopyCurrentDictionary() returned NULL.";

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

Can you add a message to the effect that logging out will probably resolve the
problem?

 
   const void* on_console = CFDictionaryGetValue(session,
                                                 kCGSessionOnConsoleKey);