[Media Router] Add experiment control logic.

extensions/common/feature_switch.cc

Index: extensions/common/feature_switch.cc
diff --git a/extensions/common/feature_switch.cc b/extensions/common/feature_switch.cc
index 5d6bb6d91738840fbacec681feaf6f70426148e9..282089936e3dfcdc67753549331c19d8174b8f1b 100644
--- a/extensions/common/feature_switch.cc
+++ b/extensions/common/feature_switch.cc
@@ -14,6 +14,7 @@ namespace extensions {
 
 namespace {
 
+const char kEnableMediaRouterExperiment[] = "EnableMediaRouter";
 const char kExtensionActionRedesignExperiment[] = "ExtensionActionRedesign";
 
 class CommonSwitches {
@@ -45,6 +46,13 @@ class CommonSwitches {
                                FeatureSwitch::DEFAULT_DISABLED),
         embedded_extension_options(switches::kEmbeddedExtensionOptions,
                                    FeatureSwitch::DEFAULT_DISABLED),
+#if defined(ENABLE_MEDIA_ROUTER)
+        // The switch enable-media-router is defined in

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

If media_router::MediaRouterEnabled simply does:
  return extensions::FeatureSwitch::media_router()->IsEnabled();
Where is Chrome's enable-media-router switch respected?

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

The flag's presence will be checked in FeatureSwitch::IsEnabled() (L187 below).
Note we passed in the flag name here but without the "enable-" prefix because we
simply pass in the flag as --enable-media-router (no =1)

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

Acknowledged.

+        // chrome/common/chrome_switches.cc, but we can't depend on chrome here.
+        media_router("media-router",
+                     kEnableMediaRouterExperiment,
+                     FeatureSwitch::DEFAULT_DISABLED),
+#endif  // defined(ENABLE_MEDIA_ROUTER)
         trace_app_source(switches::kTraceAppSource,
                          FeatureSwitch::DEFAULT_ENABLED) {
   }
@@ -65,6 +73,9 @@ class CommonSwitches {
   FeatureSwitch extension_action_redesign_override;
   FeatureSwitch scripts_require_action;
   FeatureSwitch embedded_extension_options;
+#if defined(ENABLE_MEDIA_ROUTER)
+  FeatureSwitch media_router;
+#endif
   FeatureSwitch trace_app_source;
 };
 
@@ -94,8 +105,7 @@ FeatureSwitch* FeatureSwitch::extension_action_redesign() {
   // is enabled. Should be removed when the toolbar redesign is used by default.
   // See crbug.com/514694
   // TODO(kmarshall): Remove this override.
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          "enable-media-router")) {
+  if (media_router()->IsEnabled()) {
     return &g_common_switches.Get().extension_action_redesign_override;
   }
 #endif  // defined(ENABLE_MEDIA_ROUTER)
@@ -110,6 +120,11 @@ FeatureSwitch* FeatureSwitch::embedded_extension_options() {
 FeatureSwitch* FeatureSwitch::trace_app_source() {
   return &g_common_switches.Get().trace_app_source;
 }
+#if defined(ENABLE_MEDIA_ROUTER)
+FeatureSwitch* FeatureSwitch::media_router() {
+  return &g_common_switches.Get().media_router;
+}
+#endif
 
 FeatureSwitch::ScopedOverride::ScopedOverride(FeatureSwitch* feature,
                                               bool override_value)