Construct literal maps using factory constructor.

sdk/lib/_internal/lib/js_helper.dart

Index: sdk/lib/_internal/lib/js_helper.dart
diff --git a/sdk/lib/_internal/lib/js_helper.dart b/sdk/lib/_internal/lib/js_helper.dart
index 76d615f6fbb893eff708514ede31bea01d1e04a3..06ff0b27a12c204d48e132e1078b757ca92f2705 100644
--- a/sdk/lib/_internal/lib/js_helper.dart
+++ b/sdk/lib/_internal/lib/js_helper.dart
@@ -1806,14 +1806,14 @@ int objectHashCode(var object) {
   }
 }
 
-/**
- * Called by generated code to build a map literal. [keyValuePairs] is
- * a list of key, value, key, value, ..., etc.
- */
 makeLiteralMap(keyValuePairs) {
   return fillLiteralMap(keyValuePairs, new LinkedHashMap());
 }
 
+/**
+ * Called by generated code to build a map literal. [keyValuePairs] is
+ * a list of key, value, key, value, ..., etc.
+ */
 fillLiteralMap(keyValuePairs, Map result) {
   // TODO(johnniwinther): Use JSArray to optimize this code instead of calling
   // [getLength] and [getIndex].