[Media Router] Add experiment control logic.

chrome/browser/media/router/media_router_feature.h

Index: chrome/browser/media/router/media_router_feature.h
diff --git a/chrome/browser/media/router/media_router_feature.h b/chrome/browser/media/router/media_router_feature.h
new file mode 100644
index 0000000000000000000000000000000000000000..d350bc1903719985f50e5e9b38cb35b16a680568
--- /dev/null
+++ b/chrome/browser/media/router/media_router_feature.h
@@ -0,0 +1,15 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FEATURE_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FEATURE_H_
+
+namespace media_router {
+
+// Returns true if Media Router is enabled.
+bool MediaRouterEnabled();
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FEATURE_H_