chromeos: turn on simplified display management for mash

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 51f5df159047662cf70a5b79ca5d1e7bf4df58ae..529cedd4ba34094b03c51d23347cf352253023c3 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -271,6 +271,9 @@ class ASH_EXPORT Shell : public SessionObserver,
   // Returns true if simplified display management should be enabled.
   // TODO(sky): remove this; temporary until http://crbug.com/718860 is done.
   static bool ShouldEnableSimplifiedDisplayManagement();
+  // Use this variant if you have a Config and the Shell may not have been
+  // initialized yet.
+  static bool ShouldEnableSimplifiedDisplayManagement(ash::Config config);
 
   // Creates a default views::NonClientFrameView for use by windows in the
   // Ash environment.