dbus: Mock MockObjectProxy::SetNameOwnerChangedCallback().

ObjectProxy's real method calls Bus::AssertOnOriginThread()
and causes in some log spam (but surprisingly doesn't
crash). Override the method in MockObjectProxy to prevent
this.

Also update chromeos::PowerManagerClientTest to expect this
call.

BUG=646912

Review-Url: https://codereview.chromium.org/2340683003
Cr-Commit-Position: refs/heads/master@{#418864}


CrOS-Libchrome-Original-Commit: 0ef935c2ea78249e96fb76fbc3bb91a79ab32afb
diff --git a/dbus/mock_object_proxy.h b/dbus/mock_object_proxy.h
index ee80820..17d2a9f 100644
--- a/dbus/mock_object_proxy.h
+++ b/dbus/mock_object_proxy.h
@@ -56,6 +56,8 @@
                     const std::string& signal_name,
                     SignalCallback signal_callback,
                     OnConnectedCallback on_connected_callback));
+  MOCK_METHOD1(SetNameOwnerChangedCallback,
+               void(NameOwnerChangedCallback callback));
   MOCK_METHOD1(WaitForServiceToBeAvailable,
                void(WaitForServiceToBeAvailableCallback callback));
   MOCK_METHOD0(Detach, void());