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

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 b1db3e2a3239e72676ca568f87ad9cfe411e1979..6b4ad7cb4af2f00a376732f669727e76d86d0b3a 100644
--- a/ash/common/material_design/material_design_controller.cc
+++ b/ash/common/material_design/material_design_controller.cc
@@ -54,11 +54,6 @@ bool MaterialDesignController::IsShelfMaterial() {
 }
 
 // static
-bool MaterialDesignController::IsImmersiveModeMaterial() {
-  return IsMaterial();
-}
-
-// static
 bool MaterialDesignController::IsSystemTrayMenuMaterial() {
   return IsMaterial();
 }