cros-md: Remove the non-MD immersive mode code paths

ash/common/material_design/material_design_controller.h

Index: ash/common/material_design/material_design_controller.h
diff --git a/ash/common/material_design/material_design_controller.h b/ash/common/material_design/material_design_controller.h
index 6ecdb04270b7263078b324540eb9d9974dfb7e6a..f5adc4aaa49184ac5bedd81c7332656ce4e0d97b 100644
--- a/ash/common/material_design/material_design_controller.h
+++ b/ash/common/material_design/material_design_controller.h
@@ -40,10 +40,6 @@ class ASH_EXPORT MaterialDesignController {
   // Returns true if Material Design features are enabled for Chrome OS shelf.
   static bool IsShelfMaterial();
 
-  // Returns true if Material Design features are enabled for Chrome OS
-  // immersive mode.
-  static bool IsImmersiveModeMaterial();
-
   // Returns true if Material Design features are enabled for Chrome OS system
   // tray menu.
   static bool IsSystemTrayMenuMaterial();