Replace more ObserverList with base::ObserverList.

This is everything but the chrome directory
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

[email protected] (chromeos)
[email protected] (device/bluetooth)

Review URL: https://codereview.chromium.org/1162943002

Cr-Commit-Position: refs/heads/master@{#332626}
diff --git a/components/user_manager/user_manager_base.h b/components/user_manager/user_manager_base.h
index d8454efa..7007681 100644
--- a/components/user_manager/user_manager_base.h
+++ b/components/user_manager/user_manager_base.h
@@ -396,10 +396,10 @@
   // been read from trusted device policy yet.
   std::string owner_email_;
 
-  ObserverList<UserManager::Observer> observer_list_;
+  base::ObserverList<UserManager::Observer> observer_list_;
 
   // TODO(nkostylev): Merge with session state refactoring CL.
-  ObserverList<UserManager::UserSessionStateObserver>
+  base::ObserverList<UserManager::UserSessionStateObserver>
       session_state_observer_list_;
 
   // Time at which this object was created.