Show Media Router toolbar icon ephemerally for MR dialogs

chrome/browser/ui/webui/media_router/media_router_test.h

Index: chrome/browser/ui/webui/media_router/media_router_test.h
diff --git a/chrome/browser/ui/webui/media_router/media_router_test.h b/chrome/browser/ui/webui/media_router/media_router_test.h
index 512aa290117ac7466d47445fdd2f25a72efb8dc3..cae43a9083b706925759665ba9e9899f3049271b 100644
--- a/chrome/browser/ui/webui/media_router/media_router_test.h
+++ b/chrome/browser/ui/webui/media_router/media_router_test.h
@@ -10,18 +10,29 @@
 #include "extensions/common/feature_switch.h"
 
 class BrowserWindow;
+class TestingProfile;
 
 class MediaRouterTest : public BrowserWithTestWindowTest {
  public:
+  // |require_mock_ui_service_| defaults to false in the default ctor.
   MediaRouterTest();
+  explicit MediaRouterTest(bool require_mock_ui_service);
   ~MediaRouterTest() override;
 
+  // BrowserWithTestWindowTest:
+  TestingProfile* CreateProfile() override;
+
  protected:
   // BrowserWithTestWindowTest override.
   BrowserWindow* CreateBrowserWindow() override;
 
  private:
   extensions::FeatureSwitch::ScopedOverride feature_override_;
+
+  // When this is set to true, MockMediaRouterUIService is instantiated.
+  // Otherwise, no MediaRouterUIService is instantiated.
+  bool require_mock_ui_service_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaRouterTest);
 };