diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 9faa2b6c2896..eb3e27e02724 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -3641,7 +3641,8 @@ ContentParent::Observe(nsISupports* aSubject, const char* aTopic,
     NS_LossyConvertUTF16toASCII strData(aData);
 
     // A pref changed. If it is useful to do so, inform child processes.
-    if (!ShouldSyncPreference(strData.Data())) {
+    if (!ShouldSyncPreference(strData.Data(),
+                              /* will be fixed later */ false)) {
       return NS_OK;
     }
 
diff --git a/dom/media/ipc/RDDProcessManager.cpp b/dom/media/ipc/RDDProcessManager.cpp
index ab14bab50cdc..066b60c85af2 100644
--- a/dom/media/ipc/RDDProcessManager.cpp
+++ b/dom/media/ipc/RDDProcessManager.cpp
@@ -97,7 +97,7 @@ void RDDProcessManager::OnPreferenceChange(const char16_t* aData) {
   NS_LossyConvertUTF16toASCII strData(aData);
 
   // A pref changed. If it is useful to do so, inform child processes.
-  if (!ShouldSyncPreference(strData.Data())) {
+  if (!ShouldSyncPreference(strData.Data(), false)) {
     return;
   }
 
diff --git a/gfx/ipc/GPUProcessManager.cpp b/gfx/ipc/GPUProcessManager.cpp
index e7ba83817964..c77ec9fa7c6a 100644
--- a/gfx/ipc/GPUProcessManager.cpp
+++ b/gfx/ipc/GPUProcessManager.cpp
@@ -164,7 +164,7 @@ void GPUProcessManager::OnPreferenceChange(const char16_t* aData) {
   NS_LossyConvertUTF16toASCII strData(aData);
 
   // A pref changed. If it is useful to do so, inform child processes.
-  if (!ShouldSyncPreference(strData.Data())) {
+  if (!ShouldSyncPreference(strData.Data(), false)) {
     return;
   }
 
diff --git a/gfx/vr/ipc/VRProcessManager.cpp b/gfx/vr/ipc/VRProcessManager.cpp
index 1d489d5c42e4..a6dca8db3064 100644
--- a/gfx/vr/ipc/VRProcessManager.cpp
+++ b/gfx/vr/ipc/VRProcessManager.cpp
@@ -217,7 +217,7 @@ void VRProcessManager::OnPreferenceChange(const char16_t* aData) {
   NS_LossyConvertUTF16toASCII strData(aData);
 
   // A pref changed. If it is useful to do so, inform child processes.
-  if (!ShouldSyncPreference(strData.Data())) {
+  if (!ShouldSyncPreference(strData.Data(), false)) {
     return;
   }
 
diff --git a/ipc/glue/ProcessUtils.h b/ipc/glue/ProcessUtils.h
index 023750847f82..3f28ffb89235 100644
--- a/ipc/glue/ProcessUtils.h
+++ b/ipc/glue/ProcessUtils.h
@@ -26,7 +26,7 @@ void SetThisProcessName(const char* aName);
 class SharedPreferenceSerializer final {
  public:
   explicit SharedPreferenceSerializer(
-      std::function<bool(const char*)>&& aShouldSerializeFn);
+      std::function<bool(const char*, bool)>&& aShouldSerializeFn);
   SharedPreferenceSerializer(SharedPreferenceSerializer&& aOther);
   ~SharedPreferenceSerializer();
 
@@ -48,7 +48,7 @@ class SharedPreferenceSerializer final {
   size_t mPrefsLength;
   UniqueFileHandle mPrefMapHandle;
   UniqueFileHandle mPrefsHandle;
-  std::function<bool(const char*)> mShouldSerializeFn;
+  std::function<bool(const char*, bool)> mShouldSerializeFn;
 };
 
 class SharedPreferenceDeserializer final {
diff --git a/ipc/glue/ProcessUtils_common.cpp b/ipc/glue/ProcessUtils_common.cpp
index 5dbe13cc7b2f..fd3e066b6f7f 100644
--- a/ipc/glue/ProcessUtils_common.cpp
+++ b/ipc/glue/ProcessUtils_common.cpp
@@ -18,7 +18,7 @@ namespace mozilla {
 namespace ipc {
 
 SharedPreferenceSerializer::SharedPreferenceSerializer(
-    std::function<bool(const char*)>&& aShouldSerializeFn)
+    std::function<bool(const char*, bool)>&& aShouldSerializeFn)
     : mPrefMapSize(0), mPrefsLength(0), mShouldSerializeFn(aShouldSerializeFn) {
   MOZ_COUNT_CTOR(SharedPreferenceSerializer);
 }
diff --git a/ipc/glue/UtilityProcessManager.cpp b/ipc/glue/UtilityProcessManager.cpp
index b5f11e56143d..bdb9848a29dc 100644
--- a/ipc/glue/UtilityProcessManager.cpp
+++ b/ipc/glue/UtilityProcessManager.cpp
@@ -95,7 +95,7 @@ void UtilityProcessManager::OnPreferenceChange(const char16_t* aData) {
   NS_LossyConvertUTF16toASCII strData(aData);
 
   // A pref changed. If it is useful to do so, inform child processes.
-  if (!ShouldSyncPreference(strData.Data())) {
+  if (!ShouldSyncPreference(strData.Data(), false)) {
     return;
   }
 
diff --git a/modules/libpref/Preferences.cpp b/modules/libpref/Preferences.cpp
index 6cd3271abd50..cb93307a2481 100644
--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -3588,7 +3588,7 @@ NS_IMPL_ISUPPORTS(Preferences, nsIPrefService, nsIObserver, nsIPrefBranch,
 /* static */
 void Preferences::SerializePreferences(
     nsCString& aStr,
-    const std::function<bool(const char*)>& aShouldSerializeFn) {
+    const std::function<bool(const char*, bool)>& aShouldSerializeFn) {
   MOZ_RELEASE_ASSERT(InitStaticMembers());
 
   aStr.Truncate();
@@ -3596,7 +3596,9 @@ void Preferences::SerializePreferences(
   for (auto iter = HashTable()->iter(); !iter.done(); iter.next()) {
     Pref* pref = iter.get().get();
     if (!pref->IsTypeNone() && pref->HasAdvisablySizedValues()) {
-      pref->SerializeAndAppend(aStr, !aShouldSerializeFn(pref->Name()));
+      pref->SerializeAndAppend(
+          aStr, !aShouldSerializeFn(pref->Name(),
+                                    /* will be fixed later */ false));
     }
   }
 
@@ -5673,7 +5675,7 @@ namespace mozilla {
 
 void UnloadPrefsModule() { Preferences::Shutdown(); }
 
-bool ShouldSyncPreference(const char* aPref) {
+bool ShouldSyncPreference(const char* aPref, bool aIsDestWebContentProcess) {
 #define PREF_LIST_ENTRY(s) \
   { s, (sizeof(s) / sizeof(char)) - 1 }
 struct PrefListEntry {
diff --git a/modules/libpref/Preferences.h b/modules/libpref/Preferences.h
index 044380cb9135..d953f8404ad4 100644
--- a/modules/libpref/Preferences.h
+++ b/modules/libpref/Preferences.h
@@ -401,7 +401,7 @@ class Preferences final : public nsIPrefService,
   // prefs in bulk from the parent process, via shared memory.
   static void SerializePreferences(
       nsCString& aStr,
-      const std::function<bool(const char*)>& aShouldSerializeFn);
+      const std::function<bool(const char*, bool)>& aShouldSerializeFn);
   static void DeserializePreferences(char* aStr, size_t aPrefsLen);
 
   static mozilla::ipc::FileDescriptor EnsureSnapshot(size_t* aSize);
@@ -532,7 +532,7 @@ class Preferences final : public nsIPrefService,
   static bool InitStaticMembers();
 };
 
-bool ShouldSyncPreference(const char* aPref);
+bool ShouldSyncPreference(const char* aPref, bool aIsDestWebContentProcess);
 
 }  // namespace mozilla
 
diff --git a/modules/libpref/test/gtest/Basics.cpp b/modules/libpref/test/gtest/Basics.cpp
index 8f6e0bef1fc3..4f0ee3a17d7b 100644
--- a/modules/libpref/test/gtest/Basics.cpp
+++ b/modules/libpref/test/gtest/Basics.cpp
@@ -44,10 +44,10 @@ TEST(PrefsBasics, Serialize)
 
   nsCString str;
   Preferences::SerializePreferences(
-      str, [](const char* aPref) -> bool { return false; });
+      str, [](const char* aPref, bool) -> bool { return false; });
   ASSERT_STREQ(str.Data(), "");
 
-  Preferences::SerializePreferences(str, [](const char* aPref) -> bool {
+  Preferences::SerializePreferences(str, [](const char* aPref, bool) -> bool {
     return strncmp(aPref, "foo.bool", 8) == 0;
   });
   ASSERT_STREQ(str.Data(), "B-:8/foo.bool:T:F\n");