Remove pre-MD code from PowerStatusView.

ash/common/material_design/material_design_controller.cc

Index: ash/common/material_design/material_design_controller.cc
diff --git a/ash/common/material_design/material_design_controller.cc b/ash/common/material_design/material_design_controller.cc
index dd8a25a73a4641f9a8cc22d17320b7849b8cea65..7fcfa5633102026bc8d26f7516b1a5f83723b910 100644
--- a/ash/common/material_design/material_design_controller.cc
+++ b/ash/common/material_design/material_design_controller.cc
@@ -18,9 +18,4 @@ bool MaterialDesignController::IsSystemTrayMenuMaterial() {
   return true;
 }
 
-// static
-bool MaterialDesignController::UseMaterialDesignSystemIcons() {
-  return true;
-}
-
 }  // namespace ash