Bug 1526725 - Make dom.event.default_to_passive_touch_listeners a static pref. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D56555

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

dom/events/EventListenerManager.cpp

@@ -661,24 +661,10 @@ bool EventListenerManager::ListenerCanHandle(const Listener* aListener,
   return aListener->mEventMessage == aEventMessage;
 }
 
-static bool DefaultToPassiveTouchListeners() {
-  static bool sDefaultToPassiveTouchListeners = false;
-  static bool sIsPrefCached = false;
-
-  if (!sIsPrefCached) {
-    sIsPrefCached = true;
-    Preferences::AddBoolVarCache(
-        &sDefaultToPassiveTouchListeners,
-        "dom.event.default_to_passive_touch_listeners");
-  }
-
-  return sDefaultToPassiveTouchListeners;
-}
-
 void EventListenerManager::MaybeMarkPassive(EventMessage aMessage,
                                             EventListenerFlags& aFlags) {
   if ((aMessage == eTouchStart || aMessage == eTouchMove) && mIsMainThreadELM &&
-      DefaultToPassiveTouchListeners()) {
+      StaticPrefs::dom_event_default_to_passive_touch_listeners()) {
     nsCOMPtr<nsINode> node;
     nsCOMPtr<nsPIDOMWindowInner> win;
     if ((win = GetTargetAsInnerWindow()) ||

modules/libpref/init/StaticPrefList.yaml

@@ -1456,6 +1456,12 @@
   value: true
   mirror: always
 
+# Whether touch event listeners are passive by default.
+- name: dom.event.default_to_passive_touch_listeners
+  type: bool
+  value: true
+  mirror: always
+
 # Enable clipboard readText() and writeText() by default
 - name: dom.events.asyncClipboard
   type: bool

modules/libpref/init/all.js

@@ -4679,10 +4679,6 @@ pref("dom.noopener.newprocess.enabled", true);
 // loops with faulty converters involved.
 pref("general.document_open_conversion_depth_limit", 20);
 
-// If true, touchstart and touchmove listeners on window, document,
-// documentElement and document.body are passive by default.
-pref("dom.event.default_to_passive_touch_listeners", true);
-
 // Should only be enabled in tests
 pref("dom.events.testing.asyncClipboard", false);