Fix multibuffer crashing bug

media/blink/multibuffer_reader.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_READER_H_
 #define MEDIA_BLINK_MULTIBUFFER_READER_H_
 
 #include <stdint.h>
 
 #include <limits>
@@ skipping 83 matching lines @@
   // Returns the block for a particular byte position.
   MultiBufferBlockId block(int64_t byte_pos) const {
     return byte_pos >> multibuffer_->block_size_shift();
   }
 
   // Returns the block for a particular byte position, rounding up.
   MultiBufferBlockId block_ceil(int64_t byte_pos) const {
     return block(byte_pos + (1LL << multibuffer_->block_size_shift()) - 1);
   }
 
+  // Unpin previous range, then pin the new range.
+  void PinRange(MultiBuffer::BlockId begin, MultiBuffer::BlockId end);
+
   // Check if wait operation can complete now.
   void CheckWait();
 
   // Recalculate preload_pos_ and update our entry in the multibuffer
   // reader index. Also call CheckWait(). This function is basically
   // called anything changes, like when we get more data or seek to
   // a new position.
   void UpdateInternalState();
 
   // Update end_ if p-1 contains an end-of-stream block.
@@ skipping 12 matching lines @@
 
   // Defer reading once we have this much data.
   int64_t preload_high_;
   // Stop deferring once we have this much data.
   int64_t preload_low_;
 
   // Pin this much data in the cache from the current position.
   int64_t max_buffer_forward_;
   int64_t max_buffer_backward_;
 
+  // Currently pinned range.
+  Interval<MultiBuffer::BlockId> pinned_range_;
+
   // Current position in bytes.
   int64_t pos_;
 
   // [block(pos_)..preload_pos_) are known to be in the cache.
   // preload_pos_ is only allowed to point to a filled
   // cache position if it is equal to end_ or pos_+preload_.
   // This is a pointer to a slot in the cache, so the unit is
   // blocks.
   MultiBufferBlockId preload_pos_;
 
   // True if we've requested data from the cache by calling WaitFor().
   bool loading_;
 
   // When Available() > current_wait_size_ we call cb_.
   int64_t current_wait_size_;
   base::Closure cb_;
 
   // Progress callback.
   base::Callback<void(int64_t, int64_t)> progress_callback_;
 
   base::WeakPtrFactory<MultiBufferReader> weak_factory_;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_MULTIBUFFER_READER_H_