Show Media Router toolbar icon ephemerally for MR dialogs

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 54bb2285e3658ee2ad0f0b5cc16ae22c2ef77feb..7ccfa46bcef56923c07bd2e0ffd9451b9a03d177 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -3600,6 +3600,8 @@ test("unit_tests") {
       "../browser/ui/toolbar/back_forward_menu_model_unittest.cc",
       "../browser/ui/toolbar/mock_component_toolbar_actions_factory.cc",
       "../browser/ui/toolbar/mock_component_toolbar_actions_factory.h",
+      "../browser/ui/toolbar/mock_media_router_action_controller.cc",
+      "../browser/ui/toolbar/mock_media_router_action_controller.h",
       "../browser/ui/toolbar/recent_tabs_builder_test_helper.cc",
       "../browser/ui/toolbar/recent_tabs_builder_test_helper.h",
       "../browser/ui/toolbar/recent_tabs_sub_menu_model_unittest.cc",
@@ -4329,9 +4331,9 @@ test("unit_tests") {
         "../browser/ui/webui/media_router/cast_modes_with_media_sources_unittest.cc",
         "../browser/ui/webui/media_router/media_cast_mode_unittest.cc",
         "../browser/ui/webui/media_router/media_router_dialog_controller_impl_unittest.cc",
-        "../browser/ui/webui/media_router/media_router_test.cc",
-        "../browser/ui/webui/media_router/media_router_test.h",
         "../browser/ui/webui/media_router/media_router_ui_unittest.cc",
+        "../browser/ui/webui/media_router/media_router_web_ui_test.cc",
+        "../browser/ui/webui/media_router/media_router_web_ui_test.h",
         "../browser/ui/webui/media_router/media_router_webui_message_handler_unittest.cc",
         "../browser/ui/webui/media_router/query_result_manager_unittest.cc",
       ]