Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/extension_custom_bindings.js

Index: chrome/renderer/resources/extensions/extension_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/extension_custom_bindings.js b/chrome/renderer/resources/extensions/extension_custom_bindings.js
index af1de2dc5bdd3c875dfdca5fa812523963236cf2..1e9cf190802f8cf839346e415d529c9f1bd182d5 100644
--- a/chrome/renderer/resources/extensions/extension_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/extension_custom_bindings.js
@@ -6,11 +6,11 @@
 
 (function() {
 
-native function GetChromeHidden();
-native function GetExtensionViews();
-native function OpenChannelToExtension(sourceId, targetId, name);
+var extension = requireNative('extension');
+var GetExtensionViews = extension.GetExtensionViews;
+var OpenChannelToExtension = extension.OpenChannelToExtension;
 
-var chromeHidden = GetChromeHidden();
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
 // This should match chrome.windows.WINDOW_ID_NONE.
 //