Allow extension APIs to be called from WebUI.

extensions/browser/api/test/test_api.h

 // 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.
 
 #ifndef EXTENSIONS_BROWSER_API_TEST_TEST_API_H_
 #define EXTENSIONS_BROWSER_API_TEST_TEST_API_H_
 
 #include "base/values.h"
 #include "extensions/browser/extension_function.h"
 
@@ skipping 59 matching lines @@
 };
 
 class TestSendMessageFunction : public AsyncExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("test.sendMessage", UNKNOWN)
 
   // Sends a reply back to the calling extension. Many extensions don't need
   // a reply and will just ignore it.
   void Reply(const std::string& message);
 
+  // Sends an error back to the calling extension.
+  void ReplyWithError(const std::string& error);
+
  protected:
   virtual ~TestSendMessageFunction();
 
   // ExtensionFunction:
   virtual bool RunAsync() OVERRIDE;
 };
 
 class TestGetConfigFunction : public TestExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("test.getConfig", UNKNOWN)
@@ skipping 39 matching lines @@
  protected:
   virtual ~TestWaitForRoundTripFunction();
 
   // TestExtensionFunction:
   virtual bool RunSafe() OVERRIDE;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_TEST_TEST_API_H_