[ChromeOS] Expose keyboard remapping to signin screen.

chrome/browser/chromeos/events/event_rewriter.cc

Index: chrome/browser/chromeos/events/event_rewriter.cc
diff --git a/chrome/browser/chromeos/events/event_rewriter.cc b/chrome/browser/chromeos/events/event_rewriter.cc
index d532a8b375defbef81cbecf8646c09b35647033d..da1fd869a3f9941867ff49692c2f45d49e7660fb 100644
--- a/chrome/browser/chromeos/events/event_rewriter.cc
+++ b/chrome/browser/chromeos/events/event_rewriter.cc
@@ -20,9 +20,12 @@
 #include "chrome/browser/chromeos/login/ui/login_display_host.h"
 #include "chrome/browser/extensions/extension_commands_global_registry.h"
 #include "chrome/browser/profiles/profile_manager.h"
+#include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
+#include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 #include "chrome/common/pref_names.h"
 #include "chromeos/chromeos_switches.h"
 #include "components/prefs/pref_service.h"
+#include "components/user_manager/known_user.h"
 #include "components/user_manager/user_manager.h"
 #include "ui/base/ime/chromeos/ime_keyboard.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
@@ -132,14 +135,32 @@ const ModifierRemapping* kModifierRemappingNeoMod3 = &kModifierRemappings[1];
 // prefs::kLanguageRemapSearchKeyTo.
 const ModifierRemapping* GetRemappedKey(const std::string& pref_name,
                                         const PrefService& pref_service) {
-  if (!pref_service.FindPreference(pref_name.c_str()))
-    return NULL;  // The |pref_name| hasn't been registered. On login screen?
-  const int value = pref_service.GetInteger(pref_name.c_str());
+  int value = -1;
+  // If we're at the login screen, try to get the pref from the global prefs
+  // dictionary.
+  if (LoginDisplayHost::default_host()) {
+    const AccountId focused_account_id = LoginDisplayHost::default_host()
+                                             ->GetOobeUI()
+                                             ->signin_screen_handler()
+                                             ->focused_pod_account_id();
+    if (!focused_account_id.empty()) {

[xiyuan, 2017/02/22 17:40:18]

nit: empty() -> is_valid()

+      user_manager::known_user::GetIntegerPref(focused_account_id, pref_name,
+                                               &value);

[Alexander Alekseev, 2017/02/22 10:51:50]

I am not an owner of this file, but it seems to me that this is too
login-specific for event rewriter.

Did you consider moving these new lines to:
bool SigninScreenHandler::GetKeyboardRemappingValue(
    const std::string& pref_name, 
    int* value);
?

It could return true if there is a focused pod and a preference for focused
user.

Then, it will become:

if (!LoginDisplayHost::default_host() ||
    !LoginDisplayHost::default_host()>GetOobeUI()
        ->signin_screen_handler()
        ->GetKeyboardRemappingValue(pref_name, &value)) {

  if (!pref_service.FindPreference(pref_name.c_str()))
    return NULL;  // The |pref_name| hasn't been registered.

  const int value = pref_service.GetInteger(pref_name.c_str());
}

for(...) {
}

return nullptr;
}

[xdai1, 2017/02/22 18:36:16]

Done.

+    }
+  }
+
+  if (value == -1) {
+    if (pref_service.FindPreference(pref_name))
+      value = pref_service.GetInteger(pref_name);
+    else
+      return nullptr;
+  }
+
   for (size_t i = 0; i < arraysize(kModifierRemappings); ++i) {
     if (value == kModifierRemappings[i].remap_to)
       return &kModifierRemappings[i];
   }
-  return NULL;
+  return nullptr;
 }
 
 bool HasDiamondKey() {