[Media Router] Add experiment control logic.

extensions/common/feature_switch.h

Index: extensions/common/feature_switch.h
diff --git a/extensions/common/feature_switch.h b/extensions/common/feature_switch.h
index 4e058b525e6d882d4017b17d12046d9f85fe9225..9717f1c2efa95dbc9a2a97cf7383c0a5b2361fe2 100644
--- a/extensions/common/feature_switch.h
+++ b/extensions/common/feature_switch.h
@@ -39,6 +39,9 @@ class FeatureSwitch {
   static FeatureSwitch* extension_action_redesign();
   static FeatureSwitch* scripts_require_action();
   static FeatureSwitch* embedded_extension_options();
+#if defined(ENABLE_MEDIA_ROUTER)

[msw, 2015/10/23 20:18:43]

It's unfortunate to add so many #if define blocks; is that really good/intended?

[imcheng, 2015/10/23 21:39:27]

I agree. But it helps to minimize the unnecessary code compiled into binaries if
it is not enabled. 

+  static FeatureSwitch* media_router();

[msw, 2015/10/23 20:18:43]

nit: order after non-compile-time-switched entries (and to match .cc order)

[imcheng, 2015/10/23 21:39:27]

The formatting gets a bit tricky with it being the last field in the member
initializer list. I will reorder the definition in .cc instead?

[msw, 2015/10/23 22:30:49]

Acknowledged.

+#endif
   static FeatureSwitch* trace_app_source();
 
   enum DefaultValue {