cc: Add cache purging to software image decode controller.

cc/tiles/software_image_decode_controller.h

 // Copyright 2016 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_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 #define CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 242 matching lines @@
   // called with no lock acquired and it returns nullptr if the decoding or
   // scaling failed.
   std::unique_ptr<DecodedImage> GetScaledImageDecode(
       const ImageKey& key,
       sk_sp<const SkImage> image);
 
   void SanityCheckState(int line, bool lock_acquired);
   void RefImage(const ImageKey& key);
   void RefAtRasterImage(const ImageKey& key);
   void UnrefAtRasterImage(const ImageKey& key);
+  void ReduceCacheUsageInternal(size_t max_items);
 
   // Helper function which dumps all images in a specific ImageMRUCache.
   void DumpImageMemoryForCache(const ImageMRUCache& cache,
                                const char* cache_name,
                                base::trace_event::ProcessMemoryDump* pmd) const;
 
   // Overriden from base::MemoryCoordinatorClient.
   void OnMemoryStateChange(base::MemoryState state) override;
 
   std::unordered_map<ImageKey, scoped_refptr<TileTask>, ImageKeyHash>
@@ skipping 16 matching lines @@
 
   ResourceFormat format_;
 
   // Used to uniquely identify DecodedImages for memory traces.
   base::AtomicSequenceNumber next_tracing_id_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_