[Media Router] Add experiment control logic.

chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc

Index: chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc
diff --git a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc
index 7362141a5aa5f0423f9fd7becd4048f677b1c9eb..1c40511f5efc38dedc661a8fadc6cf99ffe829f8 100644
--- a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl_browsertest.cc
@@ -25,10 +25,8 @@ class MediaRouterDialogControllerBrowserTest : public InProcessBrowserTest {
   MediaRouterDialogControllerBrowserTest()
       : dialog_controller_(nullptr),
         initiator_(nullptr),
-        media_router_dialog_(nullptr) {
-    base::CommandLine::ForCurrentProcess()->AppendSwitch(
-        switches::kEnableMediaRouter);
-  }
+        media_router_dialog_(nullptr),
+        feature_override_(FeatureSwitch::media_router(), true) {}
   ~MediaRouterDialogControllerBrowserTest() override {}
 
  protected:
@@ -55,6 +53,7 @@ class MediaRouterDialogControllerBrowserTest : public InProcessBrowserTest {
   WebContents* media_router_dialog_;
 
  private:
+  extensions::FeatureSwitch::ScopedOverride feature_override_;
   DISALLOW_COPY_AND_ASSIGN(MediaRouterDialogControllerBrowserTest);
 };