[Sync] Replace uses of ObserverListThreadSafe with WeakHandles

chrome/browser/sync/test/engine/syncer_command_test.h

Index: chrome/browser/sync/test/engine/syncer_command_test.h
diff --git a/chrome/browser/sync/test/engine/syncer_command_test.h b/chrome/browser/sync/test/engine/syncer_command_test.h
index 55460b70ecee6bfca2d9e5ab9d94c68b8d6854ed..c6fccbb21e9e5c2d2633a4ada91dbfd5e55c0d72 100644
--- a/chrome/browser/sync/test/engine/syncer_command_test.h
+++ b/chrome/browser/sync/test/engine/syncer_command_test.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/message_loop.h"
 #include "chrome/browser/sync/engine/model_safe_worker.h"
 #include "chrome/browser/sync/sessions/debug_info_getter.h"
 #include "chrome/browser/sync/sessions/sync_session.h"
@@ -157,6 +158,7 @@ class SyncerCommandTestWithParam : public testing::TestWithParam<T>,
   }
 
  private:
+  MessageLoop message_loop_;
   scoped_ptr<TestDirectorySetterUpper> syncdb_;
   scoped_ptr<sessions::SyncSessionContext> context_;
   scoped_ptr<MockConnectionManager> mock_server_;