chromeos: Makes AshTestBase/Helper target mash when appropriate

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index c819fef2168b789a4b0953fa4bb98ca7752d878a..41b0e0b1e3129dee8b11c23747a9a35a1b813d16 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -24,6 +24,7 @@ class WindowDelegate;
 }  // namespace aura
 
 namespace display {
+class Display;
 class DisplayManager;
 
 namespace test {
@@ -168,6 +169,8 @@ class AshTestBase : public testing::Test {
   // Swap the primary display with the secondary.
   void SwapPrimaryDisplay();
 
+  display::Display GetSecondaryDisplay();
+
  private:
   friend class ash::AshTestImplAura;