Use container::back() and container::pop_back() in ui/

ui/display/mac/screen_mac.mm

Index: ui/display/mac/screen_mac.mm
diff --git a/ui/display/mac/screen_mac.mm b/ui/display/mac/screen_mac.mm
index 2b89f9183fb0e8e6994be67604e20a0ab4e609a7..a158b79edb6718d6c3d354bc23cd019805aa9fc2 100644
--- a/ui/display/mac/screen_mac.mm
+++ b/ui/display/mac/screen_mac.mm
@@ -235,10 +235,8 @@ class ScreenMac : public Screen {
       }
     }
 
-    if (!displays.size())
-      return std::vector<Display>(1, GetPrimaryDisplay());
-
-    return displays;
+    return displays.empty() ? std::vector<Display>(1, GetPrimaryDisplay())
+                            : displays;
   }
 
   // The displays currently attached to the device.