Clear Image Decode Cache on Navigation

cc/tiles/image_decode_cache.h

 // Copyright 2015 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 CC_TILES_IMAGE_DECODE_CACHE_H_
 #define CC_TILES_IMAGE_DECODE_CACHE_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/paint/draw_image.h"
 #include "cc/tiles/decoded_draw_image.h"
@@ skipping 75 matching lines @@
                                      const DecodedDrawImage& decoded_image) = 0;
 
   // This function informs the cache that now is a good time to clean up
   // memory. This is called periodically from the compositor thread.
   virtual void ReduceCacheUsage() = 0;
 
   // This function informs the cache that we are hidden and should not be
   // retaining cached resources longer than needed.
   virtual void SetShouldAggressivelyFreeResources(
       bool aggressively_free_resources) = 0;
+
+  // Clears all elements from the cache.
+  virtual void ClearCache() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_DECODE_CACHE_H_