chromeos: Remove AshTestBase::SupportsMultipleDisplays

ash/common/test/ash_test.cc

Index: ash/common/test/ash_test.cc
diff --git a/ash/common/test/ash_test.cc b/ash/common/test/ash_test.cc
index 3afcf64ed0c8dadcb84d530a756a26c4e8e2eac5..245ce6b5b67fe5139236eaed08b9a02b22a06f42 100644
--- a/ash/common/test/ash_test.cc
+++ b/ash/common/test/ash_test.cc
@@ -48,10 +48,6 @@ test::TestSystemTrayDelegate* AshTest::GetSystemTrayDelegate() {
       WmShell::Get()->system_tray_delegate());
 }
 
-bool AshTest::SupportsMultipleDisplays() const {
-  return test_impl_->SupportsMultipleDisplays();
-}
-
 void AshTest::UpdateDisplay(const std::string& display_spec) {
   return test_impl_->UpdateDisplay(display_spec);
 }