Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/tts_engine_custom_bindings.js

Index: chrome/renderer/resources/extensions/tts_engine_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/tts_engine_custom_bindings.js b/chrome/renderer/resources/extensions/tts_engine_custom_bindings.js
index 85e36b083f59408172998d3db5afe1b61170e5a2..a9429b035d60bd3a318fe3de0f29ffd865658a83 100644
--- a/chrome/renderer/resources/extensions/tts_engine_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/tts_engine_custom_bindings.js
@@ -4,9 +4,7 @@
 
 // Custom bindings for the ttsEngine API.
 
-(function() {
-
-native function GetChromeHidden();
+var GetChromeHidden = natives.GetChromeHidden;
 
 GetChromeHidden().registerCustomHook('ttsEngine', function() {
   chrome.ttsEngine.onSpeak.dispatch = function(text, options, requestId) {
@@ -17,5 +15,3 @@ GetChromeHidden().registerCustomHook('ttsEngine', function() {
         this, [text, options, sendTtsEvent]);
   };
 });
-
-})();