Bug 1610974 - Use designated initializers consistently in LookAndFeelInt r=hiro

To avoid a clang-10 failure with `error: mixture of designated and non-designated initializers in the same initializer list is a C99 extension [-Werror,-Wc99-designator]`

Differential Revision: https://phabricator.services.mozilla.com/D61133

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

widget/android/nsLookAndFeel.cpp

@@ -528,7 +528,8 @@ nsTArray<LookAndFeelInt> nsLookAndFeel::GetIntCacheImpl() {
   const IntID kIdsToCache[] = {eIntID_PrefersReducedMotion};
 
   for (IntID id : kIdsToCache) {
-    lookAndFeelIntCache.AppendElement(LookAndFeelInt{id, .value = GetInt(id)});
+    lookAndFeelIntCache.AppendElement(
+        LookAndFeelInt{.id = id, .value = GetInt(id)});
   }
 
   return lookAndFeelIntCache;

widget/gtk/nsLookAndFeel.cpp

@@ -291,7 +291,8 @@ nsTArray<LookAndFeelInt> nsLookAndFeel::GetIntCacheImpl() {
                                eIntID_UseAccessibilityTheme};
 
   for (IntID id : kIdsToCache) {
-    lookAndFeelIntCache.AppendElement(LookAndFeelInt{id, .value = GetInt(id)});
+    lookAndFeelIntCache.AppendElement(
+        LookAndFeelInt{.id = id, .value = GetInt(id)});
   }
 
   return lookAndFeelIntCache;