chromeos: Remove AshTestBase::SupportsMultipleDisplays

ash/test/ash_test_impl_aura.cc

Index: ash/test/ash_test_impl_aura.cc
diff --git a/ash/test/ash_test_impl_aura.cc b/ash/test/ash_test_impl_aura.cc
index 2a19c3fd0259b8aaedb41a2080e59534a00dfc9c..ec4fa7843c5bbbf5024bfa9ecf5940431228185e 100644
--- a/ash/test/ash_test_impl_aura.cc
+++ b/ash/test/ash_test_impl_aura.cc
@@ -51,10 +51,6 @@ void AshTestImplAura::TearDown() {
   ash_test_base_->TearDown();
 }
 
-bool AshTestImplAura::SupportsMultipleDisplays() const {
-  return ash_test_base_->SupportsMultipleDisplays();
-}
-
 void AshTestImplAura::UpdateDisplay(const std::string& display_spec) {
   ash_test_base_->UpdateDisplay(display_spec);
 }