Bug 1873526: Refactor the restriction override list from a big if statement to a list r=KrisWright

Differential Revision: https://phabricator.services.mozilla.com/D198081

modules/libpref/Preferences.cpp

@@ -6024,7 +6024,8 @@ struct PrefListEntry {
 //      StaticPrefList.yml), a string pref, and it is NOT exempted in
 //      sDynamicPrefOverrideList
 //
-// This behavior is codified in ShouldSanitizePreference() below
+// This behavior is codified in ShouldSanitizePreference() below.
+// Exclusions of preferences can be defined in sOverrideRestrictionsList[].
 static const PrefListEntry sRestrictFromWebContentProcesses[] = {
     // Remove prefs with user data
     PREF_LIST_ENTRY("datareporting.policy."),
@@ -6073,6 +6074,15 @@ static const PrefListEntry sRestrictFromWebContentProcesses[] = {
     PREF_LIST_ENTRY("toolkit.telemetry.previousBuildID"),
 };
 
+// Allowlist for prefs and branches blocklisted in
+// sRestrictFromWebContentProcesses[], including prefs from
+// StaticPrefList.yaml and *.js, to let them pass.
+static const PrefListEntry sOverrideRestrictionsList[]{
+    PREF_LIST_ENTRY("services.settings.clock_skew_seconds"),
+    PREF_LIST_ENTRY("services.settings.last_update_seconds"),
+    PREF_LIST_ENTRY("services.settings.server"),
+};
+
 // These prefs are dynamically-named (i.e. not specified in prefs.js or
 // StaticPrefList) and would normally by blocklisted but we allow them through
 // anyway, so this override list acts as an allowlist
@@ -6168,10 +6178,12 @@ static bool ShouldSanitizePreference(const Pref* const aPref) {
   // pref through.
   for (const auto& entry : sRestrictFromWebContentProcesses) {
     if (strncmp(entry.mPrefBranch, prefName, entry.mLen) == 0) {
-      const auto* p = prefName;  // This avoids clang-format doing ugly things.
-      return !(strncmp("services.settings.clock_skew_seconds", p, 36) == 0 ||
-               strncmp("services.settings.last_update_seconds", p, 37) == 0 ||
-               strncmp("services.settings.server", p, 24) == 0);
+      for (const auto& pasEnt : sOverrideRestrictionsList) {
+        if (strncmp(pasEnt.mPrefBranch, prefName, pasEnt.mLen) == 0) {
+          return false;
+        }
+      }
+      return true;
     }
   }