Add a TestBrowserDialog helper class for testing browser dialogs in a consistent way.

ui/base/test/material_design_controller_test_api.h

Index: ui/base/test/material_design_controller_test_api.h
diff --git a/ui/base/test/material_design_controller_test_api.h b/ui/base/test/material_design_controller_test_api.h
index 3eb53a349f5585ad03e677b5e84478335a66b271..09cbc6748e256e21c75453afb33cbec6ff177281 100644
--- a/ui/base/test/material_design_controller_test_api.h
+++ b/ui/base/test/material_design_controller_test_api.h
@@ -19,12 +19,17 @@ class MaterialDesignControllerTestAPI {
   explicit MaterialDesignControllerTestAPI(MaterialDesignController::Mode mode);
   ~MaterialDesignControllerTestAPI();
 
+  // Force the given |value| for IsSecondaryUiMaterial() for the lifetime of the
+  // test API.
+  void SetSecondaryUiMaterial(bool value);
+
   // Wrapper functions for MaterialDesignController internal functions.
   static void Uninitialize();
 
  private:
   const MaterialDesignController::Mode previous_mode_;
   const bool previous_initialized_;
+  const bool previous_include_secondary_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MaterialDesignControllerTestAPI);
 };