Bug 1882482 - Collect media.eme.enabled. r=tjr

Differential Revision: https://phabricator.services.mozilla.com/D202935

toolkit/components/resistfingerprinting/metrics.yaml

@@ -373,3 +373,21 @@ characteristics:
     expires: never
     data_sensitivity:
       - interaction
+
+  prefs_media_eme_enabled:
+    type: boolean
+    description: >
+      Value of the media.eme.enabled pref.
+    lifetime: application
+    send_in_pings:
+      - user-characteristics
+    notification_emails:
+      - tom@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1879151
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1882482
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1882482#c6
+    expires: never
+    data_sensitivity:
+      - interaction

toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp

@@ -13,6 +13,8 @@
 #include "mozilla/glean/GleanPings.h"
 #include "mozilla/glean/GleanMetrics.h"
 
+#include "mozilla/StaticPrefs_media.h"
+
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/PreferenceSheet.h"
 #include "mozilla/RelativeLuminanceUtils.h"
@@ -123,6 +125,9 @@ void PopulatePrefs() {
   mozilla::Preferences::GetLocalizedCString("intl.accept_languages",
                                             acceptLang);
   mozilla::glean::characteristics::prefs_intl_accept_languages.Set(acceptLang);
+
+  mozilla::glean::characteristics::prefs_media_eme_enabled.Set(
+      mozilla::StaticPrefs::media_eme_enabled());
 }
 
 // ==================================================================