Move nsimage_cache into base so that it can be accessed from outside of chrome

chrome/browser/cocoa/nsimage_cache.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_COCOA_NSIMAGE_CACHE_H_
-#define CHROME_BROWSER_COCOA_NSIMAGE_CACHE_H_
-
-#import <Cocoa/Cocoa.h>
-
-namespace nsimage_cache {
-
-// Returns an autoreleased image from the main app bundle
-// (mac_util::MainAppBundle()) 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.
-NSImage *ImageNamed(NSString* name);
-
-// Clears the cache.
-void Clear(void);
-
-}  // namespace nsimage_cache
-
-#endif  // CHROME_BROWSER_COCOA_NSIMAGE_CACHE_H_