[Media Router] Add experiment control logic.

extensions/common/feature_switch.cc

 // Copyright 2013 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 "extensions/common/feature_switch.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
 #include "extensions/common/switches.h"
 
 namespace extensions {
 
 namespace {
 
+const char kEnableMediaRouterExperiment[] = "EnableMediaRouter";
 const char kExtensionActionRedesignExperiment[] = "ExtensionActionRedesign";
 
 class CommonSwitches {
  public:
   CommonSwitches()
       : easy_off_store_install(nullptr, FeatureSwitch::DEFAULT_DISABLED),
         force_dev_mode_highlighting(switches::kForceDevModeHighlighting,
                                     FeatureSwitch::DEFAULT_DISABLED),
         prompt_for_external_extensions(
 #if defined(CHROMIUM_BUILD)
@@ skipping 11 matching lines @@
                                      FeatureSwitch::DEFAULT_DISABLED),
         extension_action_redesign(switches::kExtensionActionRedesign,
                                   kExtensionActionRedesignExperiment,
                                   FeatureSwitch::DEFAULT_DISABLED),
         extension_action_redesign_override(switches::kExtensionActionRedesign,
                                            FeatureSwitch::DEFAULT_ENABLED),
         scripts_require_action(switches::kScriptsRequireAction,
                                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) {
   }
 
   // Enables extensions to be easily installed from sites other than the web
   // store.
   FeatureSwitch easy_off_store_install;
 
   FeatureSwitch force_dev_mode_highlighting;
 
   // Should we prompt the user before allowing external extensions to install?
   // Default is yes.
   FeatureSwitch prompt_for_external_extensions;
 
   FeatureSwitch error_console;
   FeatureSwitch enable_override_bookmarks_ui;
   FeatureSwitch extension_action_redesign;
   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;
 };
 
 base::LazyInstance<CommonSwitches> g_common_switches =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 FeatureSwitch* FeatureSwitch::force_dev_mode_highlighting() {
   return &g_common_switches.Get().force_dev_mode_highlighting;
 }
 FeatureSwitch* FeatureSwitch::easy_off_store_install() {
   return &g_common_switches.Get().easy_off_store_install;
 }
 FeatureSwitch* FeatureSwitch::prompt_for_external_extensions() {
   return &g_common_switches.Get().prompt_for_external_extensions;
 }
 FeatureSwitch* FeatureSwitch::error_console() {
   return &g_common_switches.Get().error_console;
 }
 FeatureSwitch* FeatureSwitch::enable_override_bookmarks_ui() {
   return &g_common_switches.Get().enable_override_bookmarks_ui;
 }
 FeatureSwitch* FeatureSwitch::extension_action_redesign() {
 #if defined(ENABLE_MEDIA_ROUTER)
   // Force-enable the redesigned extension action toolbar when the Media Router
   // 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)
   return &g_common_switches.Get().extension_action_redesign;
 }
 FeatureSwitch* FeatureSwitch::scripts_require_action() {
   return &g_common_switches.Get().scripts_require_action;
 }
 FeatureSwitch* FeatureSwitch::embedded_extension_options() {
   return &g_common_switches.Get().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)
     : feature_(feature),
       previous_value_(feature->GetOverrideValue()) {
   feature_->SetOverrideValue(
       override_value ? OVERRIDE_ENABLED : OVERRIDE_DISABLED);
 }
 
 FeatureSwitch::ScopedOverride::~ScopedOverride() {
@@ skipping 76 matching lines @@
 
 void FeatureSwitch::SetOverrideValue(OverrideValue override_value) {
   override_value_ = override_value;
 }
 
 FeatureSwitch::OverrideValue FeatureSwitch::GetOverrideValue() const {
   return override_value_;
 }
 
 }  // namespace extensions