Fix a typo in webview_custom_bindings.js

BUG=140315
Test=None, this bindings is not exposed yet.

Review URL: https://codereview.chromium.org/189923003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255840 0039d316-1c4b-4281-b951-d872f2087c98

chrome/renderer/resources/extensions/webview_custom_bindings.js

@@ -99,7 +99,8 @@ binding.registerCustomHook(function(bindingsAPI) {
     var instanceId = request.args[0];
     var id = request.args[1];
     if (request.args[2].onclick) {
-      contextMenus.handlersForId(instanceId, id)[id] = request.args[2].onclick;
+      webviewContextMenus.handlersForId(instanceId, id)[id] =
+          request.args[2].onclick;
     }
   });