chromeos: Remove AshTestBase::SupportsMultipleDisplays

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index a0ad32b599a6da1860f9c6f825d42638dc2edf9a..69f5942326fbf8f95df9bdba0d020424058cba8f 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -198,11 +198,6 @@ display::Display::Rotation AshTestBase::GetCurrentInternalDisplayRotation() {
 }
 
 // static
-bool AshTestBase::SupportsMultipleDisplays() {
-  return AshTestHelper::SupportsMultipleDisplays();
-}
-
-// static
 void AshTestBase::UpdateDisplay(const std::string& display_specs) {
   display::test::DisplayManagerTestApi(Shell::GetInstance()->display_manager())
       .UpdateDisplay(display_specs);