ChromeOS: implement per-user time zone preferences.

chrome/browser/chromeos/login/screens/network_screen.cc

Index: chrome/browser/chromeos/login/screens/network_screen.cc
diff --git a/chrome/browser/chromeos/login/screens/network_screen.cc b/chrome/browser/chromeos/login/screens/network_screen.cc
index 5fa9d2dca3ccbccff7e575477df82221ca1043d9..2facf72c8c06c935216aabd7ecba21bbb4ad48ea 100644
--- a/chrome/browser/chromeos/login/screens/network_screen.cc
+++ b/chrome/browser/chromeos/login/screens/network_screen.cc
@@ -20,6 +20,7 @@
 #include "chrome/browser/chromeos/login/screens/network_view.h"
 #include "chrome/browser/chromeos/login/ui/input_events_blocker.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
+#include "chrome/browser/chromeos/system/timezone_util.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/webui/chromeos/login/l10n_util.h"
 #include "chrome/common/pref_names.h"
@@ -132,12 +133,20 @@ std::string NetworkScreen::GetInputMethod() const {
 }
 
 void NetworkScreen::SetTimezone(const std::string& timezone_id) {
-  std::string current_timezone_id;
-  CrosSettings::Get()->GetString(kSystemTimezone, &current_timezone_id);
-  if (current_timezone_id == timezone_id || timezone_id.empty())
-    return;
-  timezone_ = timezone_id;
-  CrosSettings::Get()->SetString(kSystemTimezone, timezone_id);
+  if (system::PerUserTimezoneEnabled()) {
+    if (timezone_id.empty())
+      return;
+
+    timezone_ = timezone_id;
+    chromeos::system::SetSystemAndSigninScreenTimezone(timezone_id);

[stevenjb, 2017/05/25 22:13:06]

Could we make this do the test and call CrosSettings::Get()->SetString if
system::PerUserTimezoneEnabled() is false instead?

[Alexander Alekseev, 2017/05/29 21:10:23]

SetSystemAndSigninScreenTimezone() is setting timezone directly (via
system::TimezoneSettings). CrosSettings interface is designed to be used for UI
API and does additional checks.

If I make this change, CrosSettings API will also be used in the other places,
where it could be wrong. On the contrary, replacing CrosSettings with
system::TimezoneSettings call will not exactly mimic the old behavior here.

[stevenjb, 2017/05/30 16:47:18]

I was suggesting:

SetSystemAndSigninScreenTimezone(const std::string& timezone) {
  if (!PerUserTimezoneEnabled()) {
    ... execute lines 143-149 from this file and return
  }
}

And remove the if() in line 136. timezone_util already accesses CrosSettings so
it wouldn't add any new dependencies there and it would simplify this UI code.
It doesn't look like that would impact any other calls to
SetSystemAndSigninScreenTimezone(), but perhaps I missed a call in which case I
guess this is fine as-is.

[Alexander Alekseev, 2017/07/06 06:30:28]

You're righ. Even more, SetSystemAndSigninScreenTimezone() seems to do exactly
the same as lines 143-148 now, so we can simply drop PerUserTimezoneEnabled()
check here.

+  } else {
+    std::string current_timezone_id;
+    CrosSettings::Get()->GetString(kSystemTimezone, &current_timezone_id);
+    if (current_timezone_id == timezone_id || timezone_id.empty())
+      return;
+    timezone_ = timezone_id;
+    CrosSettings::Get()->SetString(kSystemTimezone, timezone_id);
+  }
 }
 
 std::string NetworkScreen::GetTimezone() const {