fixes #157, renaming local library identifiers if needed.

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 5dc4609ebb2f59a9bbbb71912ad4057af3d847a9..55a2d9744068a508837801095127ec21691c1f3c 100644
--- a/test/codegen/expect/dir/html_input_c.js
+++ b/test/codegen/expect/dir/html_input_c.js
@@ -1,5 +1,6 @@
-var html_input_c;
-(function(exports) {
+var html_input_c = dart.defineLibrary(html_input_c, {});
+var html_input_e = dart.import(html_input_e);
+(function(exports, html_input_e) {
   'use strict';
   dart.defineLazyProperties(exports, {
     get y() {
@@ -7,4 +8,4 @@ var html_input_c;
     },
     set y(_) {}
   });
-})(html_input_c || (html_input_c = {}));
+})(html_input_c, html_input_e);