Add browser tests for extensions tab API.

chrome/browser/extensions/extension_test_api.h

 // Copyright (c) 2009 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_TEST_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_TEST_API_H_
 
 #include "chrome/browser/extensions/extension_function.h"
 
 // Function names.
 namespace extension_test_api_functions {
   extern const char kPassFunction[];
   extern const char kFailFunction[];
+  extern const char kLogFunction[];
 };  // namespace extension_test_api_functions
 
 class ExtensionTestPassFunction : public SyncExtensionFunction {
   virtual bool RunImpl();
 };
 
 class ExtensionTestFailFunction : public SyncExtensionFunction {
   virtual bool RunImpl();
 };
 
+class ExtensionTestLogFunction : public SyncExtensionFunction {
+  virtual bool RunImpl();
+};
+
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_TEST_API_H_
+