ui: Export a function that's used by a test.

ui/gfx/mac/nsimage_cache.h

 // Copyright (c) 2011 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 UI_GFX_MAC_NSIMAGE_CACHE_H_
 #define UI_GFX_MAC_NSIMAGE_CACHE_H_
 #pragma once
 
 #include "ui/base/ui_export.h"
 
@@ skipping 10 matching lines @@
 // Returns an autoreleased image from the framework bundle
 // (base::mac::FrameworkBundle()) with the given name, and keeps it in memory so
 // future fetches are fast.
 // NOTE:
 //   - This should only be called on the main thread.
 //   - The caller should retain the image if they want to keep it around, as
 //     the cache could have limit on size/lifetime, etc.
 UI_EXPORT NSImage* GetCachedImageWithName(NSString* name);
 
 // Clears the image cache.
-void ClearCachedImages(void);
+UI_EXPORT void ClearCachedImages(void);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_MAC_NSIMAGE_CACHE_H_