Media Engagement: implement shell of the media engagement service.

media/base/media_switches.cc

Index: media/base/media_switches.cc
diff --git a/media/base/media_switches.cc b/media/base/media_switches.cc
index b6de64a285451dbb1d39eb7584665a534616af51..8fcd483753d5b10667380ca29d2de7b119ca061b 100644
--- a/media/base/media_switches.cc
+++ b/media/base/media_switches.cc
@@ -222,6 +222,11 @@ const base::Feature kVideoBlitColorAccuracy{"video-blit-color-accuracy",
 const base::Feature kExternalClearKeyForTesting{
     "external-clear-key-for-testing", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables Media Engagement Index recording in order to bypass autoplay
+// policies.
+const base::Feature kMediaEngagement{"media-engagement",
+                                     base::FEATURE_DISABLED_BY_DEFAULT};
+
 #if defined(OS_ANDROID)
 // Lock the screen orientation when a video goes fullscreen.
 const base::Feature kVideoFullscreenOrientationLock{