We should switch the keyboard layout to the layout the user set according to

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 449b5eeb5400aa3a01190ef1375b150dd5435fc0..2a1bea3a6957fa693b0f5b658de6c0bdb3cd2133 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -5,11 +5,13 @@
 #include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 
 #include "base/callback.h"
+#include "base/chromeos/chromeos_version.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
+#include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_util.h"
@@ -19,6 +21,7 @@
 #include "chrome/browser/browser_process_platform_part_chromeos.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/chromeos/app_mode/kiosk_app_manager.h"
+#include "chrome/browser/chromeos/input_method/input_method_util.h"
 #include "chrome/browser/chromeos/kiosk_mode/kiosk_mode_settings.h"
 #include "chrome/browser/chromeos/login/hwid_checker.h"
 #include "chrome/browser/chromeos/login/login_display_host_impl.h"
@@ -103,6 +106,12 @@ void ClearDnsCache(IOThread* io_thread) {
   io_thread->ClearHostCache();
 }
 
+static bool Contains(const std::vector<std::string>& container,
+                     const std::string& value) {
+  return std::find(container.begin(), container.end(), value) !=
+         container.end();
+}
+
 }  // namespace
 
 namespace chromeos {
@@ -812,6 +821,10 @@ void SigninScreenHandler::RegisterMessages() {
               &SigninScreenHandler::HandleUpdateOfflineLogin);
 }
 
+void SigninScreenHandler::RegisterPrefs(PrefRegistrySimple* registry) {
+  registry->RegisterDictionaryPref(prefs::kUsersLRUInputMethod);
+}
+
 void SigninScreenHandler::HandleGetUsers() {
   SendUserList(false);
 }
@@ -968,6 +981,109 @@ void SigninScreenHandler::OnDnsCleared() {
   ShowSigninScreenIfReady();
 }
 
+void SigninScreenHandler::SetUserInputMethodHWDefault() {
+#if defined(OS_CHROMEOS)

[Nikita (slow), 2013/07/11 09:13:54]

No need for OS_CHROMEOS here as this class is already located in chromeos
specific folder.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+  chromeos::input_method::InputMethodManager* manager =
+      chromeos::input_method::InputMethodManager::Get();
+  manager->ChangeInputMethod(
+      manager->GetInputMethodUtil()->GetHardwareInputMethodId());
+#endif
+}
+
+void SigninScreenHandler::SetUserInputMethod(const std::string& username) {
+#if defined(OS_CHROMEOS)

[Nikita (slow), 2013/07/11 09:13:54]

nit: same here.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+  // Update keyboard layout to least recently used by the user
+  if (g_browser_process == NULL)

[Nikita (slow), 2013/07/11 09:13:54]

nit: drop this check.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+    return;
+
+  if (!base::chromeos::IsRunningOnChromeOS())

[Nikita (slow), 2013/07/11 09:13:54]

What about relying on stubs instead when not running on a real Chrome OS VM
image/device?

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+    return;
+
+  PrefService* local_state = g_browser_process->local_state();
+  DCHECK(local_state);

[Nikita (slow), 2013/07/11 09:13:54]

nit: Drop this DCHECK.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+
+  if (local_state == NULL)

[Nikita (slow), 2013/07/11 09:13:54]

nit: Drop this.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+    return;
+
+  chromeos::input_method::InputMethodManager* manager =
+      chromeos::input_method::InputMethodManager::Get();
+  DCHECK(manager);

[Nikita (slow), 2013/07/11 09:13:54]

nit: Drop this DCHECK.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+
+  bool succeed = false;
+  do {

[Nikita (slow), 2013/07/11 09:13:54]

You should delete this loop it is not really needed.
My proposal:

Have a utility method that tries to switch to user specific input method and
returns bool. Code that calls it will switch to default if needed.

Introducing this method will also help split this method into smaller parts.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+    const base::DictionaryValue* users_lru_input_methods =
+        local_state->GetDictionary(prefs::kUsersLRUInputMethod);
+
+    if (users_lru_input_methods == NULL) {
+      DLOG(WARNING) << "SetUserInputMethod('" << username

[Nikita (slow), 2013/07/11 09:13:54]

nit: I guess it is perfectly normal situation till at least one user signs in
that has latin-based input_methods.

No need for DLOG(WARNING) here.

[Alexander Alekseev, 2013/07/12 20:10:49]

Do all our users always have some latin input method enabled ?
Probably HW-default is always enabled, I think.

+                    << "'): no kUsersLRUInputMethod";
+      break;
+    }
+
+    std::string input_method;
+
+    if (!users_lru_input_methods->GetStringWithoutPathExpansion(
+            username, &input_method)) {
+      DLOG(WARNING) << "SetUserInputMethod('" << username

[Nikita (slow), 2013/07/11 09:13:54]

nit: Same here. This looks like a perfectly normal (rare but normal) situation
so no need for DLOG(WARNING).

[Alexander Alekseev, 2013/07/12 20:10:49]

But it's debug log, isn't it? I think I'd better have a trace of rare events at
least in debug log.

+                    << "'): no input method for this user";
+      break;
+    }
+
+    if (manager == NULL)

[Nikita (slow), 2013/07/11 09:13:54]

You don't have to check for manager not being NULL. It is assumed it is always
not NULL when we are accessing it. You could check its lifetime if you want.

If this assumption is not true this code better crash and generate crash report
instead of doing nothing.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+      break;
+
+    const chromeos::input_method::InputMethodUtil* ime_util =
+        manager->GetInputMethodUtil();
+    DCHECK(ime_util);

[Nikita (slow), 2013/07/11 09:13:54]

nit: Drop DCHECK

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+
+    if (ime_util == NULL)

[Nikita (slow), 2013/07/11 09:13:54]

Same here.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+      return;
+
+    if (input_method.empty())
+      break;
+
+    if (!manager->IsLanguageFullLatinKeyboard(
+            ime_util->GetLanguageCodeFromInputMethodId(input_method))) {
+      LOG(WARNING) << "SetUserInputMethod('" << username

[Nikita (slow), 2013/07/11 09:13:54]

nit: I propose dropping log message as well and just doing pref cleanup instead.

[Alexander Alekseev, 2013/07/12 20:10:49]

It is probably dangerous to silently drop user preferences. I've added pref
cleanup, but left log message. Do you think it is OK now?

+                   << "'): stored user LRU input method '" << input_method
+                   << "' is no longer Full Latin Keyboard Language."
+                   << " Use hardware default instead.";
+
+      break;
+    }
+
+    if (!Contains(chromeos::input_method::InputMethodManager::Get()
+                      ->GetActiveInputMethodIds(),

[Nikita (slow), 2013/07/11 09:13:54]

nit: -> should be on the previous line

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+                  input_method)) {
+      if (!chromeos::input_method::InputMethodManager::Get()->EnableInputMethod(

[Nikita (slow), 2013/07/11 09:13:54]

nit:

if (!chromeos::input_method::InputMethodManager::Get()->
        EnableInputMethod(input_method)) {

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+              input_method)) {
+        DLOG(ERROR) << "SigninScreenHandler::SetUserInputMethod('" << username
+                    << "'): user input method '" << input_method
+                    << "' is not enabled and enabling failed (ignored!).";
+      }
+    }
+    chromeos::input_method::InputMethodManager::Get()->ChangeInputMethod(

[Nikita (slow), 2013/07/11 09:13:54]

nit: this looks more readable:

chromeos::input_method::InputMethodManager::Get()->
    ChangeInputMethod(input_method);

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+        input_method);
+
+    succeed = true;
+  } while (false);
+
+  // This is also a case when LRU layout is set only for a few local users,
+  // thus others need to be switched to default locale.
+  // Otherwise they will end up using another user's locale to log in.
+  if (!succeed) {
+    DLOG(WARNING)

[Nikita (slow), 2013/07/11 09:13:54]

nit: No need for DLOG(WARNING), perfectly normal situation.

[Alexander Alekseev, 2013/07/12 20:10:49]

But it's debug log. Let's leave traces of rare events at least in debug log.

+        << "SetUserInputMethod('" << username
+        << "'): failed to set user layout. Switching to default '"
+        << (manager != NULL
+                ? manager->GetInputMethodUtil()->GetHardwareInputMethodId()
+                : "NULL") << "'";
+
+    SetUserInputMethodHWDefault();
+  }
+#endif
+}
+
 void SigninScreenHandler::ShowSigninScreenIfReady() {
   if (!dns_cleared_ || !cookies_cleared_ || !delegate_)
     return;
@@ -989,6 +1105,10 @@ void SigninScreenHandler::ShowSigninScreenIfReady() {
   else
     delegate_->LoadWallpaper(email_);
 
+  // Set Least Recently used input method for the user

[Mattias Nissler (ping if slow), 2013/07/11 10:05:49]

nit: missing period.

[Alexander Alekseev, 2013/07/12 20:10:49]

Done.

+  if (!email_.empty())
+    SetUserInputMethod(email_);
+
   LoadAuthExtension(!gaia_silent_load_, false, false);
   UpdateUIState(UI_STATE_GAIA_SIGNIN, NULL);
 
@@ -1201,6 +1321,7 @@ void SigninScreenHandler::HandleShowAddUser(const base::ListValue* args) {
         &SigninScreenHandler::ShowSigninScreenIfReady,
         weak_factory_.GetWeakPtr()));
   }
+  SetUserInputMethodHWDefault();
 }
 
 void SigninScreenHandler::HandleToggleEnrollmentScreen() {