Make isEmpty a getter.

lib/html/scripts/idlrenderer.dart

Index: lib/html/scripts/idlrenderer.dart
diff --git a/lib/html/scripts/idlrenderer.dart b/lib/html/scripts/idlrenderer.dart
index e62c4a77fc4731a81fadfb157916c83f13eae8a2..3bf37204282f50a8e170237250751906ff883785 100644
--- a/lib/html/scripts/idlrenderer.dart
+++ b/lib/html/scripts/idlrenderer.dart
@@ -75,13 +75,13 @@ render(idl_node, [indent_str='  ']) {
       w(node.extAttrs);
       w('interface ${node.id}');
       indented(() {
-          if (!node.parents.isEmpty()) {
+          if (!node.parents.isEmpty) {
             wln(' :');
             w(node.parents, ',\n');
           }
           wln(' {');
           section(list, comment) {
-            if (list != null && !list.isEmpty()) {
+            if (list != null && !list.isEmpty) {
               wln();
               wln(comment);
               w(sort(list));
@@ -100,7 +100,7 @@ render(idl_node, [indent_str='  ']) {
       for (var name in sorted(node.map.getKeys())) {
         IDLAnnotation annotation = node.map[name];
         var args = annotation.map;
-        if (args.isEmpty()) {
+        if (args.isEmpty) {
           w('@$name');
         } else {
           var formattedArgs = [];
@@ -116,7 +116,7 @@ render(idl_node, [indent_str='  ']) {
         w(' ');
       }
     } else if (node is IDLExtAttrs) {
-      if(!node.map.isEmpty()) {
+      if(!node.map.isEmpty) {
         w('[');
         var sep = null;
         for (var name in sorted(node.map.getKeys())) {
@@ -149,7 +149,7 @@ render(idl_node, [indent_str='  ']) {
     } else if (node is IDLOperation) {
       w(node.annotations);
       w(node.extAttrs);
-      if (node.specials != null && !node.specials.isEmpty()) {
+      if (node.specials != null && !node.specials.isEmpty) {
         w(node.specials, ' ');
         w(' ');
       }