Reduce FakeArcBridgeService usage.

components/arc/test/fake_arc_bridge_service.cc

Index: components/arc/test/fake_arc_bridge_service.cc
diff --git a/components/arc/test/fake_arc_bridge_service.cc b/components/arc/test/fake_arc_bridge_service.cc
index 444492a2ef2a80ee11a512cabba3fbf67682a61c..b54c81b1770738d2c3627a7c9b64a1bd48832fa1 100644
--- a/components/arc/test/fake_arc_bridge_service.cc
+++ b/components/arc/test/fake_arc_bridge_service.cc
@@ -34,8 +34,4 @@ void FakeArcBridgeService::SetStopped() {
     SetState(State::STOPPED);
 }
 
-bool FakeArcBridgeService::HasObserver(const Observer* observer) {
-  return observer_list().HasObserver(observer);
-}
-
 }  // namespace arc