mash: Migrate ShelfLayoutManager ScreenUtil usage to ash common types.

ash/aura/wm_shell_aura.cc

Index: ash/aura/wm_shell_aura.cc
diff --git a/ash/aura/wm_shell_aura.cc b/ash/aura/wm_shell_aura.cc
index 1881d36b4a3aa3835d67325a8ede5fee068a842a..e5e067dc323ac24b7d0fa7aa35432b52e6a9b0b2 100644
--- a/ash/aura/wm_shell_aura.cc
+++ b/ash/aura/wm_shell_aura.cc
@@ -96,6 +96,16 @@ bool WmShellAura::IsActiveDisplayId(int64_t display_id) const {
   return Shell::GetInstance()->display_manager()->IsActiveDisplayId(display_id);
 }
 
+display::Display WmShellAura::GetFirstDisplay() const {
+  return Shell::GetInstance()
+      ->display_manager()
+      ->software_mirroring_display_list()[0];
+}
+
+bool WmShellAura::IsInUnifiedMode() const {
+  return Shell::GetInstance()->display_manager()->IsInUnifiedMode();
+}
+
 bool WmShellAura::IsForceMaximizeOnFirstRun() {
   return delegate()->IsForceMaximizeOnFirstRun();
 }