Bug 1626388 - Convert layout.framevisibility.enabled to a static pref r=njn

Converts `layout.framevisibility.enabled` to a static pref.

Differential Revision: https://phabricator.services.mozilla.com/D69598

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

layout/base/PresShell.cpp

@@ -5820,16 +5820,8 @@ void PresShell::DoUpdateApproximateFrameVisibility(bool aRemoveOnly) {
 }
 
 bool PresShell::AssumeAllFramesVisible() {
-  static bool sFrameVisibilityEnabled = true;
-  static bool sFrameVisibilityPrefCached = false;
-
-  if (!sFrameVisibilityPrefCached) {
-    Preferences::AddBoolVarCache(&sFrameVisibilityEnabled,
-                                 "layout.framevisibility.enabled", true);
-    sFrameVisibilityPrefCached = true;
-  }
-
-  if (!sFrameVisibilityEnabled || !mPresContext || !mDocument) {
+  if (!StaticPrefs::layout_framevisibility_enabled() || !mPresContext ||
+      !mDocument) {
     return true;
   }
 

modules/libpref/init/StaticPrefList.yaml

@@ -6016,6 +6016,12 @@
   value: true
   mirror: always
 
+# Whether frame visibility tracking is enabled globally.
+- name: layout.framevisibility.enabled
+  type: bool
+  value: true
+  mirror: always
+
 # The fraction of the scrollport we allow to horizontally scroll by before we
 # schedule an update of frame visibility.
 - name: layout.framevisibility.amountscrollbeforeupdatehorizontal

modules/libpref/init/all.js

@@ -918,9 +918,6 @@ pref("nglayout.enable_drag_images", true);
 pref("nglayout.debug.paint_flashing", false);
 pref("nglayout.debug.paint_flashing_chrome", false);
 
-// Whether frame visibility tracking is enabled globally.
-pref("layout.framevisibility.enabled", true);
-
 pref("layout.framevisibility.numscrollportwidths", 0);
 pref("layout.framevisibility.numscrollportheights", 1);