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 ef8011aefb57d363ad73bb517534ef1a1a749108..dee01d328f9da4da71fb644aa1464496e3b00e41 100644
--- a/chrome/renderer/resources/extensions/tts_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/tts_custom_bindings.js
@@ -4,12 +4,10 @@
 
 // Custom bindings for the tts API.
 
-(function() {
+var ttsNatives = requireNative('tts');
+var GetNextTTSEventId = ttsNatives.GetNextTTSEventId;
 
-native function GetChromeHidden();
-native function GetNextTTSEventId();
-
-var chromeHidden = GetChromeHidden();
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
 chromeHidden.registerCustomHook('tts', function(api) {
   var apiFunctions = api.apiFunctions;
@@ -42,5 +40,3 @@ chromeHidden.registerCustomHook('tts', function(api) {
     return id;
   });
 });
-
-})();