Makes MaterialDesignController initialization explicit

ash/test/ash_test_helper.cc

Index: ash/test/ash_test_helper.cc
diff --git a/ash/test/ash_test_helper.cc b/ash/test/ash_test_helper.cc
index f5a27b4d7bf175c55301c76c9fac8eb0012b3bb2..38f41434d7f1503ba0137e6485a20f8ba7c68c95 100644
--- a/ash/test/ash_test_helper.cc
+++ b/ash/test/ash_test_helper.cc
@@ -24,6 +24,8 @@
 #include "ui/aura/test/env_test_helper.h"
 #include "ui/aura/test/event_generator_delegate_aura.h"
 #include "ui/base/ime/input_method_initializer.h"
+#include "ui/base/material_design/material_design_controller.h"
+#include "ui/base/test/material_design_controller_test_api.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
 #include "ui/compositor/test/context_factories_for_test.h"
 #include "ui/message_center/message_center.h"
@@ -113,6 +115,10 @@ void AshTestHelper::SetUp(bool start_session) {
   }
   ShellContentState::SetInstance(content_state);
 
+  // ContentTestSuiteBase might have already initialized
+  // MaterialDesignController in unit_tests suite.
+  ui::test::MaterialDesignControllerTestAPI::UninitializeMode();
+  ui::MaterialDesignController::Initialize();
   ShellInitParams init_params;
   init_params.delegate = test_shell_delegate_;
   init_params.context_factory = context_factory;