Set Ash material design mode in tests properly

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index 288dbb54d30c6abc2f0a8ec531779556dcaed702..13de45402b956ef988da29c573f701af890209bd 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <string>
 
+#include "ash/common/material_design/material_design_controller.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
@@ -138,6 +139,12 @@ class AshTestBase : public testing::Test {
 
   void set_start_session(bool start_session) { start_session_ = start_session; }
 
+  // Sets material mode for the test. This will override material mode set via
+  // command line switches.
+  void set_material_mode(MaterialDesignController::Mode material_mode) {

[tdanderson, 2016/07/29 15:16:50]

optional nit: consider calling this set_material_mode_for_test() or similar to
make it extra clear at call sites. If you do that, perhaps change
|material_mode_| to |material_mode_for_test_|.

[mohsen, 2016/07/29 18:05:19]

This whole class is for testing purposes. What would be the point of adding
for_test suffix to this one?

+    material_mode_ = material_mode;
+  }
+
   AshTestHelper* ash_test_helper() { return ash_test_helper_.get(); }
 
   void RunAllPendingInMessageLoop();
@@ -170,6 +177,7 @@ class AshTestBase : public testing::Test {
   bool teardown_called_;
   // |SetUp()| doesn't activate session if this is set to false.
   bool start_session_;
+  MaterialDesignController::Mode material_mode_;
   std::unique_ptr<content::TestBrowserThreadBundle> thread_bundle_;
   std::unique_ptr<AshTestHelper> ash_test_helper_;
   std::unique_ptr<ui::test::EventGenerator> event_generator_;