Check for duplicate library names

test/codegen/expect/dir/html_input_c.js

Index: test/codegen/expect/dir/html_input_c.js
diff --git a/test/codegen/expect/dir/html_input_c.js b/test/codegen/expect/dir/html_input_c.js
index 55a2d9744068a508837801095127ec21691c1f3c..1b45d42a23c241ab90ed2ab27bdaed8b6dd37b9d 100644
--- a/test/codegen/expect/dir/html_input_c.js
+++ b/test/codegen/expect/dir/html_input_c.js
@@ -1,6 +1,7 @@
-var html_input_c = dart.defineLibrary(html_input_c, {});
-var html_input_e = dart.import(html_input_e);
-(function(exports, html_input_e) {
+dart.library('dir/html_input_c.js', null, /* Imports */[
+  'dir/html_input_e.js'
+], /* Lazy imports */[
+], function(exports, html_input_e) {
   'use strict';
   dart.defineLazyProperties(exports, {
     get y() {
@@ -8,4 +9,4 @@ var html_input_e = dart.import(html_input_e);
     },
     set y(_) {}
   });
-})(html_input_c, html_input_e);
+});