Bug 1703205 - Don't query AlertNotificationOrigin from RemoteLookAndFeel. r=cmartin

Since it's not read by child processes and it seems it might be
expensive to get on windows.

Differential Revision: https://phabricator.services.mozilla.com/D110908

widget/RemoteLookAndFeel.cpp

@@ -64,6 +64,17 @@ void RemoteLookAndFeel::SetDataImpl(FullLookAndFeel&& aData) {
 
 namespace {
 
+// Some lnf values are somewhat expensive to get, and are not needed in child
+// processes, so we can avoid querying them.
+bool IsNeededInChildProcess(LookAndFeel::IntID aId) {
+  switch (aId) {
+    case LookAndFeel::IntID::AlertNotificationOrigin:
+      return false;  // see bug 1703205
+    default:
+      return true;
+  }
+}
+
 template <typename Item, typename UInt, typename ID>
 Result<const Item*, nsresult> MapLookup(const nsTArray<Item>& aItems,
                                         const nsTArray<UInt>& aMap, ID aID) {
@@ -119,6 +130,10 @@ nsresult RemoteLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
 }
 
 nsresult RemoteLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
+  MOZ_DIAGNOSTIC_ASSERT(
+      IsNeededInChildProcess(aID),
+      "Querying value that we didn't bother getting from the parent process!");
+
   const int32_t* result;
   MOZ_TRY_VAR(result, MapLookup(mTables.ints(), mTables.intMap(), aID));
   aResult = *result;
@@ -158,6 +173,9 @@ static bool AddIDsToMap(nsXPLookAndFeel* aImpl, FullLookAndFeel* aLf,
 
   bool anyFromOtherTheme = false;
   for (auto id : MakeEnumeratedRange(IntID::End)) {
+    if (!IsNeededInChildProcess(id)) {
+      continue;
+    }
     if (aDifferentTheme && aImpl->FromParentTheme(id) != aFromParentTheme) {
       anyFromOtherTheme = true;
       continue;