Generate constants in server as we do in plugin

pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart

Index: pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart
diff --git a/pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart b/pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart
index c8d1c733bf440fd37ff3fda18b2a02bbf3386d21..223d59b54df74097dd9a3ae5bc56a4ffa64cd9c1 100644
--- a/pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart
+++ b/pkg/analyzer_plugin/tool/spec/codegen_protocol_constants.dart
@@ -124,12 +124,22 @@ class _ConstantVisitor extends HierarchicalApiVisitor {
     }
     type.fields.forEach((TypeObjectField field) {
       String name = field.name;
-      String fieldConstantName = parentName + '_' + name.toUpperCase();
+      List<String> components = <String>[];
+      components.add(parentName);
+      components.addAll(_split(name));
+      String fieldConstantName = _fromComponents(components);
       constants.add(new _Constant(fieldConstantName, "'$name'"));
     });
   }
 
   /**
+   * Return a name generated by converting each of the given [components] to an
+   * uppercase equivalent, then joining them with underscores.
+   */
+  String _fromComponents(List<String> components) =>
+      components.map((String component) => component.toUpperCase()).join('_');
+
+  /**
    * Generate a name from the [domainName], [kind] and [name] components.
    */
   String _generateName(String domainName, String kind, String name) {
@@ -137,9 +147,7 @@ class _ConstantVisitor extends HierarchicalApiVisitor {
     components.addAll(_split(domainName));
     components.add(kind);
     components.addAll(_split(name));
-    return components
-        .map((String component) => component.toUpperCase())
-        .join('_');
+    return _fromComponents(components);
   }
 
   /**