Delete unused themes from disk on shutdown.

chrome/browser/browser_theme_provider.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_BROWSER_THEME_PROVIDER_H_
 #define CHROME_BROWSER_BROWSER_THEME_PROVIDER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 318 matching lines @@
 
   // Save the paths of data we have written to disk in prefs.
   void SaveCachedImageData() const;
 
   // Save the id of the last theme installed.
   void SaveThemeID(const std::string& id);
 
   // Frees generated images and clears the image cache.
   void ClearCaches();
 
+  // Remove preference values for themes that are no longer in use.
+  void RemoveUnusedThemes();
+
   // Encode image at image_cache_[id] as PNG and write to disk.
   void WriteImagesToDisk() const;
 
   // Do we have a custom frame image or custom tints?
   bool ShouldTintFrames() const;
 
 #if defined(OS_LINUX)
   // Loads an image and flips it horizontally if |rtl_enabled| is true.
   GdkPixbuf* GetPixbufImpl(int id, bool rtl_enabled) const;
 #endif
@@ skipping 33 matching lines @@
   // If true, process all images; if false, just load from disk.
   bool process_images_;
 
   // Where we will store our generated images.
   FilePath image_dir_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserThemeProvider);
 };
 
 #endif  // CHROME_BROWSER_BROWSER_THEME_PROVIDER_H_