Bug 1570212 - Convert media.video_stats.enabled to a static pref. r=jya

Also remove HTMLVideoElement::InitStatics(), which is no longer needed.

Differential Revision: https://phabricator.services.mozilla.com/D40340

--HG--
extra : moz-landing-system : lando

dom/html/HTMLVideoElement.cpp

@@ -51,8 +51,6 @@ nsGenericHTMLElement* NS_NewHTMLVideoElement(
 namespace mozilla {
 namespace dom {
 
-static bool sVideoStatsEnabled;
-
 nsresult HTMLVideoElement::Clone(mozilla::dom::NodeInfo* aNodeInfo,
                                  nsINode** aResult) const {
   *aResult = nullptr;
@@ -417,14 +415,10 @@ bool HTMLVideoElement::SetVisualCloneSource(
 }
 
 /* static */
-void HTMLVideoElement::InitStatics() {
-  Preferences::AddBoolVarCache(&sVideoStatsEnabled,
-                               "media.video_stats.enabled");
+bool HTMLVideoElement::IsVideoStatsEnabled() {
+  return StaticPrefs::media_video_stats_enabled();
 }
 
-/* static */
-bool HTMLVideoElement::IsVideoStatsEnabled() { return sVideoStatsEnabled; }
-
 double HTMLVideoElement::TotalPlayTime() const {
   double total = 0.0;
 

dom/html/HTMLVideoElement.h

@@ -44,8 +44,6 @@ class HTMLVideoElement final : public HTMLMediaElement {
                               nsAttrValue& aResult) override;
   NS_IMETHOD_(bool) IsAttributeMapped(const nsAtom* aAttribute) const override;
 
-  static void InitStatics();
-
   virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction()
       const override;
 

layout/build/nsLayoutStatics.cpp

@@ -265,8 +265,6 @@ nsresult nsLayoutStatics::Initialize() {
   nsCookieService::AppClearDataObserverInit();
   nsApplicationCacheService::AppClearDataObserverInit();
 
-  HTMLVideoElement::InitStatics();
-
 #ifdef MOZ_XUL
   nsMenuBarListener::InitializeStatics();
 #endif

modules/libpref/init/StaticPrefList.yaml

@@ -5058,6 +5058,12 @@
 #endif
   mirror: always
 
+# Are video stats enabled? (Disabling can help prevent fingerprinting.)
+- name: media.video_stats.enabled
+  type: bool
+  value: true
+  mirror: always
+
 # Opus
 - name: media.opus.enabled
   type: RelaxedAtomicBool

modules/libpref/init/all.js

@@ -456,9 +456,6 @@ pref("media.video-queue.default-size", 10);
 // By default, send all of them.
 pref("media.video-queue.send-to-compositor-size", 9999);
 
-// Whether to disable the video stats to prevent fingerprinting
-pref("media.video_stats.enabled", true);
-
 // Log level for cubeb, the audio input/output system. Valid values are
 // "verbose", "normal" and "" (log disabled).
 pref("media.cubeb.logging_level", "");