[Media Router] Add experiment control logic.

chrome/test/media_router/media_router_base_browsertest.cc

Index: chrome/test/media_router/media_router_base_browsertest.cc
diff --git a/chrome/test/media_router/media_router_base_browsertest.cc b/chrome/test/media_router/media_router_base_browsertest.cc
index b89970a6c37648e3498c00d103b7645597e49bb8..03ba3d1c4ac8d56e090bad24c09c904736fcd6da 100644
--- a/chrome/test/media_router/media_router_base_browsertest.cc
+++ b/chrome/test/media_router/media_router_base_browsertest.cc
@@ -28,9 +28,9 @@ const char kExtensionUnpacked[] = "extension-unpacked";
 namespace media_router {
 
 MediaRouterBaseBrowserTest::MediaRouterBaseBrowserTest()
-    : extension_load_event_(false, false), extension_host_created_(false) {
-  base::CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableMediaRouter);
+    : extension_load_event_(false, false),
+      extension_host_created_(false),
+      feature_override_(extensions::FeatureSwitch::media_router(), true) {
   base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
       switches::kEnableExperimentalWebPlatformFeatures, "Presentation");
 }