ChromeOS: implement per-user time zone preferences.

chrome/common/pref_names.h

Index: chrome/common/pref_names.h
diff --git a/chrome/common/pref_names.h b/chrome/common/pref_names.h
index dfd317681c6760a66d77640d928574ed47fa3ab3..13f91692649a89864acc8d884837b35cc6a4699e 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -205,6 +205,7 @@ extern const char kPrimaryMouseButtonRight[];
 extern const char kMouseSensitivity[];
 extern const char kTouchpadSensitivity[];
 extern const char kUse24HourClock[];
+extern const char kUserTimezone[];
 extern const char kResolveTimezoneByGeolocation[];
 // TODO(yusukes): Change "kLanguageABC" to "kABC". The current form is too long
 // to remember and confusing. The prefs are actually for input methods and i18n
@@ -747,6 +748,7 @@ extern const char kFactoryResetRequested[];
 extern const char kDebuggingFeaturesRequested[];
 
 #if defined(OS_CHROMEOS)
+extern const char kSigninScreenTimezone[];
 extern const char kResolveDeviceTimezoneByGeolocation[];
 extern const char kSystemTimezoneAutomaticDetectionPolicy[];
 #endif  // defined(OS_CHROMEOS)