mac: Remove IsOSLion().

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 9bdb884c3e1744b73834065343b8c4da63c26f2b..88f1f83ca086d5877f95d25ec98aa156979cb70d 100644
--- a/remoting/host/curtain_mode_mac.cc
+++ b/remoting/host/curtain_mode_mac.cc
@@ -115,20 +115,6 @@ SessionWatcher::~SessionWatcher() {
 }
 
 void SessionWatcher::ActivateCurtain() {
-  // Curtain mode causes problems with the login screen on Lion only (starting
-  // with 10.7.3), so disable it on that platform. There is a work-around, but
-  // it involves modifying a system Plist pertaining to power-management, so
-  // it's not something that should be done automatically. For more details,
-  // see https://discussions.apple.com/thread/3209415?start=690&tstart=0
-  //
-  // TODO(jamiewalch): If the underlying OS bug is ever fixed, we should support
-  // curtain mode on suitable versions of Lion.
-  if (base::mac::IsOSLion()) {
-    LOG(ERROR) << "Host curtaining is not supported on Mac OS X 10.7.";
-    DisconnectSession(protocol::ErrorCode::HOST_CONFIGURATION_ERROR);
-    return;
-  }
-
   // Try to install the switch-in handler. Do this before switching out the
   // current session so that the console session is not affected if it fails.
   if (!InstallEventHandler()) {