[Mojo Video Capture] Hook up video capture service behind a feature flag

services/video_capture/public/cpp/constants.cc

Index: services/video_capture/public/cpp/constants.cc
diff --git a/services/video_capture/public/cpp/constants.cc b/services/video_capture/public/cpp/constants.cc
new file mode 100644
index 0000000000000000000000000000000000000000..37a25edead570750b55f64b77fe0ba003c7a1913
--- /dev/null
+++ b/services/video_capture/public/cpp/constants.cc
@@ -0,0 +1,12 @@
+// Copyright 2017 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.
+
+#include "services/video_capture/public/cpp/constants.h"
+
+namespace video_capture {
+
+const base::Feature kMojoVideoCapture{"MojoVideoCapture",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
+
+}  // namespace video_capture