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 90a87ecdfd6959daabe152ef4a66d25924fb3c09..6507564af5710f8bdc7fb3ba3adf4ef977dea96a 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -209,6 +209,7 @@ 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
@@ -756,6 +757,7 @@ 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)