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

chrome/browser/cocoa/web_drag_source.mm

 // 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.
 
 #import "chrome/browser/cocoa/web_drag_source.h"
 
 #include "base/file_util.h"
+#include "base/nsimage_cache_mac.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "base/task.h"
 #include "base/thread.h"
 #include "chrome/browser/browser_process.h"
-#include "chrome/browser/cocoa/nsimage_cache.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/browser/tab_contents/tab_contents_view_mac.h"
 #include "net/base/file_stream.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_util.h"
 #import "third_party/mozilla/include/NSPasteboard+Utils.h"
 #include "webkit/glue/webdropdata.h"
 
 using base::SysNSStringToUTF8;
@@ skipping 333 matching lines @@
   if (!dropData_->plain_text.empty())
     [pasteboard_ addTypes:[NSArray arrayWithObject:NSStringPboardType]
                     owner:contentsView_];
 }
 
 - (NSImage*)dragImage {
   return MakeDragImage(dropData_.get());
 }
 
 @end  // @implementation WebDragSource (Private)