Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/tts_custom_bindings.js

Index: chrome/renderer/resources/extensions/tts_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/tts_custom_bindings.js b/chrome/renderer/resources/extensions/tts_custom_bindings.js
index 55cc36210cb40a37d2acbf510b7a3e0215b692bf..8befe1a2d375609ee77691ca3ce5c03b18fe4751 100644
--- a/chrome/renderer/resources/extensions/tts_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/tts_custom_bindings.js
@@ -4,10 +4,8 @@
 
 // Custom bindings for the tts API.
 
-(function() {
-
-native function GetChromeHidden();
-native function GetNextTTSEventId();
+var GetChromeHidden = natives.GetChromeHidden;
+var GetNextTTSEventId = natives.GetNextTTSEventId;
 
 var chromeHidden = GetChromeHidden();
 
@@ -42,5 +40,3 @@ chromeHidden.registerCustomHook('tts', function(api) {
     return id;
   });
 });
-
-})();