Lazily prune the multibuffer block cache.

media/blink/multibuffer.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 MEDIA_BLINK_MULTIBUFFER_H_
 #define MEDIA_BLINK_MULTIBUFFER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 119 matching lines @@
   class MEDIA_BLINK_EXPORT GlobalLRU : public base::RefCounted<GlobalLRU> {
    public:
     typedef MultiBufferGlobalBlockId GlobalBlockId;
     GlobalLRU();
 
     // Free elements from cache if needed and possible.
     // Don't free more than |max_to_free| blocks.
     // Virtual for testing purposes.
     void Prune(int64_t max_to_free);
 
+    // Returns true if some blocks are prunable.
+    bool Pruneable() const;
+
     void IncrementDataSize(int64_t blocks);
     void IncrementMaxSize(int64_t blocks);
 
     // LRU operations.
     void Use(MultiBuffer* multibuffer, MultiBufferBlockId id);
     void Remove(MultiBuffer* multibuffer, MultiBufferBlockId id);
     void Insert(MultiBuffer* multibuffer, MultiBufferBlockId id);
     bool Contains(MultiBuffer* multibuffer, MultiBufferBlockId id);
     int64_t Size() const;
 
    private:
     friend class base::RefCounted<GlobalLRU>;
     ~GlobalLRU();
 
+    // Schedule background pruning, if needed.
+    void SchedulePrune();
+
+    // Perform background pruning.
+    void PruneTask();
+
     // Max number of blocks.
     int64_t max_size_;
 
     // Sum of all multibuffer::data_.size().
     int64_t data_size_;
 
+    // True if there is a call to the background pruning outstanding.
+    bool background_pruning_active_;
+
     // The LRU should contain all blocks which are not pinned from
     // all multibuffers.
     LRU<GlobalBlockId> lru_;
   };
 
   MultiBuffer(int32_t block_size_shift,
               const scoped_refptr<GlobalLRU>& global_lru);
   virtual ~MultiBuffer();
 
   // Identifies a block in the cache.
@@ skipping 141 matching lines @@
   // and 0 for all blocks that are not. Used to quickly figure out
   // ranges of available/unavailable blocks without iterating.
   IntervalMap<BlockId, int32_t> present_;
 
   DISALLOW_COPY_AND_ASSIGN(MultiBuffer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_MULTIBUFFER_H_