ChromeOS user_manager: move all KnownUser code to separate file.

chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc

Index: chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
diff --git a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
index 763f5b25187ada90745c5f72deeb8b8ec67282a1..0d4812f965055e461031aac613a6ec2a0658cbb6 100644
--- a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
+++ b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
@@ -188,15 +188,4 @@ UserFlow* FakeChromeUserManager::GetDefaultUserFlow() const {
   return default_flow_.get();
 }
 
-bool FakeChromeUserManager::FindKnownUserPrefs(
-    const AccountId& account_id,
-    const base::DictionaryValue** out_value) {
-  return false;
-}
-
-void FakeChromeUserManager::UpdateKnownUserPrefs(
-    const AccountId& account_id,
-    const base::DictionaryValue& values,
-    bool clear) {}
-
 }  // namespace chromeos