chromeos: Add delay between screen off and lock.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 42c4232821d8767ce899fc8aefb6189955e05728..9a97373094b73fc401547a6b289aee21e92b4617 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -774,7 +774,10 @@ const char kLabsAdvancedFilesystemEnabled[] =
 // A boolean pref which turns on the mediaplayer.
 const char kLabsMediaplayerEnabled[] = "settings.labs.mediaplayer";
 
-// A boolean pref that turns on screen locker.
+// A boolean pref that controls whether the screen will be locked just
+// before the system is suspended or after the inactivity delays specified
+// by kPowerAcScreenLockDelayMs and kPowerBatteryScreenLockDelayMs have
+// elapsed.
 const char kEnableScreenLock[] = "settings.enable_screen_lock";
 
 // A boolean pref of whether to show mobile plan notifications.
@@ -832,7 +835,8 @@ const char kSessionLengthLimit[] = "session.length_limit";
 // the screen should be dimmed, turned off, or locked, before an
 // IdleActionImminent D-Bus signal should be sent, or before
 // kPowerIdleAction should be performed.  0 disables the delay (N/A for
-// kPowerAcIdleDelayMs).
+// kPowerAcIdleDelayMs).  kPowerAcScreenLockDelayMs is only honored when
+// kEnableScreenLock is set to true.
 const char kPowerAcScreenDimDelayMs[] = "power.ac_screen_dim_delay_ms";
 const char kPowerAcScreenOffDelayMs[] = "power.ac_screen_off_delay_ms";
 const char kPowerAcScreenLockDelayMs[] = "power.ac_screen_lock_delay_ms";