Add a mimeHandler extension API.

extensions/renderer/resources/binding.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var Event = require('event_bindings').Event;
 var forEach = require('utils').forEach;
 var GetAvailability = requireNative('v8_context').GetAvailability;
 var exceptionHandler = require('uncaught_exception_handler');
 var lastError = require('lastError');
 var logActivity = requireNative('activityLogger');
@@ skipping 59 matching lines @@
   return this.setHook_(apiName, 'handleRequest', function() {
       var name = prefix + '.' + apiName;
       logActivity.LogAPICall(extensionId, name, $Array.slice(arguments));
       var stack = exceptionHandler.getExtensionStackTrace();
       var callback = arguments[arguments.length - 1];
       var args = $Array.slice(arguments, 0, arguments.length - 1);
       var keepAlivePromise = requireAsync('keep_alive').then(function(module) {
         return module.createKeepAlive();
       });
       $Function.apply(customizedFunction, this, args).then(function(result) {
-        sendRequestHandler.safeCallbackApply(
-            name, {'stack': stack}, callback, [result]);
+        if (callback) {
+          sendRequestHandler.safeCallbackApply(name, {'stack': stack}, callback,
+                                               [result]);
+        }
       }).catch(function(error) {
-        var message = exceptionHandler.safeErrorToString(error, true);
-        lastError.run(name, message, stack, callback);
+        if (callback) {
+          var message = exceptionHandler.safeErrorToString(error, true);
+          lastError.run(name, message, stack, callback);
+        }
       }).then(function() {
         keepAlivePromise.then(function(keepAlive) {
           keepAlive.close();
         });
       });
     });
 };
 
 APIFunctions.prototype.setUpdateArgumentsPostValidate =
     function(apiName, customizedFunction) {
@@ skipping 384 matching lines @@
                     availability.message);
       return;
     }
 
     this.runHooks_(mod);
     return mod;
   }
 };
 
 exports.Binding = Binding;