[Sync] Replace uses of ObserverListThreadSafe with WeakHandles

chrome/browser/sync/engine/syncer_proto_util_unittest.cc

Index: chrome/browser/sync/engine/syncer_proto_util_unittest.cc
diff --git a/chrome/browser/sync/engine/syncer_proto_util_unittest.cc b/chrome/browser/sync/engine/syncer_proto_util_unittest.cc
index a22e1a37431be8fa2c70f52956fab5789a74e023..809ce1e81c4a218d88706eeea96f03efdab26c49 100644
--- a/chrome/browser/sync/engine/syncer_proto_util_unittest.cc
+++ b/chrome/browser/sync/engine/syncer_proto_util_unittest.cc
@@ -8,6 +8,7 @@
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/message_loop.h"
 #include "chrome/browser/sync/engine/syncproto.h"
 #include "chrome/browser/sync/syncable/blob.h"
 #include "chrome/browser/sync/syncable/directory_manager.h"
@@ -137,6 +138,7 @@ class SyncerProtoUtilTest : public testing::Test {
   }
 
  protected:
+  MessageLoop message_loop_;
   browser_sync::TestDirectorySetterUpper setter_upper_;
 };