Fix "unused variable" warnings.

content/test/mock_keyboard.h

 // Copyright (c) 2012 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 CONTENT_TEST_MOCK_KEYBOARD_H_
 #define CONTENT_TEST_MOCK_KEYBOARD_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 78 matching lines @@
   // layout, key code, and modifiers, i.e. characters returned when we type
   // specified keys on a specified layout.
   // This function returns the length of Unicode characters filled in the
   // |output| parameter.
   int GetCharacters(Layout layout,
                     int key_code,
                     Modifiers modifiers,
                     std::wstring* output);
 
  private:
-  Layout keyboard_layout_;
-  Modifiers keyboard_modifiers_;
-
 #if defined(OS_WIN)
+  Layout keyboard_layout_ = LAYOUT_NULL;
+  Modifiers keyboard_modifiers_ = INVALID;
   MockKeyboardDriverWin driver_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(MockKeyboard);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_TEST_MOCK_KEYBOARD_H_