Convert //ash from scoped_ptr to std::unique_ptr

ash/test/display_manager_test_api.h

Index: ash/test/display_manager_test_api.h
diff --git a/ash/test/display_manager_test_api.h b/ash/test/display_manager_test_api.h
index b72818c90c40c9dd8b1ea2e6e2ac8dfe43b088a0..b28a63cc77e3b1bc1c31e21fc3c150e734835e7b 100644
--- a/ash/test/display_manager_test_api.h
+++ b/ash/test/display_manager_test_api.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -98,7 +99,7 @@ void SwapPrimaryDisplay();
 // independent of current displays, use DisplayLayoutBuilder or simply
 // create a new DisplayLayout and set display id fields (primary, ids
 // in placement) manually.
-scoped_ptr<display::DisplayLayout> CreateDisplayLayout(
+std::unique_ptr<display::DisplayLayout> CreateDisplayLayout(
     display::DisplayPlacement::Position position,
     int offset);