Gut ash::MaterialDesignController, and remove the about:flags entry.

ash/test/ash_test_helper.h

Index: ash/test/ash_test_helper.h
diff --git a/ash/test/ash_test_helper.h b/ash/test/ash_test_helper.h
index eb6657ce2db4e924c81ad7bbc3876bb737a9b447..448beff5414e37eafb1358abc16e7543636e884b 100644
--- a/ash/test/ash_test_helper.h
+++ b/ash/test/ash_test_helper.h
@@ -7,8 +7,6 @@
 
 #include <memory>
 
-#include "ash/common/material_design/material_design_controller.h"
-#include "ash/common/test/material_design_controller_test_api.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 
@@ -42,10 +40,7 @@ class AshTestHelper {
 
   // Creates the ash::Shell and performs associated initialization.  Set
   // |start_session| to true if the user should log in before the test is run.
-  // |material_mode| determines the material design mode to be used for the
-  // tests. If |material_mode| is UNINITIALIZED, the value from command line
-  // switches is used.
-  void SetUp(bool start_session, MaterialDesignController::Mode material_mode);
+  void SetUp(bool start_session);
 
   // Destroys the ash::Shell and performs associated cleanup.
   void TearDown();
@@ -86,8 +81,6 @@ class AshTestHelper {
   // Check if Bluez DBus Manager was initialized here.
   bool bluez_dbus_manager_initialized_;
 
-  std::unique_ptr<test::MaterialDesignControllerTestAPI> material_design_state_;
-
   DISALLOW_COPY_AND_ASSIGN(AshTestHelper);
 };