Add support for complete buffer discards.

media/base/decoder_buffer.h

 // Copyright (c) 2012 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_BASE_DECODER_BUFFER_H_
 #define MEDIA_BASE_DECODER_BUFFER_H_
 
 #include <string>
 #include <utility>
 
@@ skipping 90 matching lines @@
     return side_data_.get();
   }
 
   int side_data_size() const {
     DCHECK(!end_of_stream());
     return side_data_size_;
   }
 
   // A discard window indicates the amount of data which should be discard from
   // this buffer after decoding.  The first value is the amount of the front and
-  // the second the amount off the back.
+  // the second the amount off the back.  A value of kInfiniteDuration() for the
+  // first value indicates the entire buffer should be discarded; the second
+  // value must be base::TimeDelta() in this case.
   typedef std::pair<base::TimeDelta, base::TimeDelta> DiscardPadding;
   const DiscardPadding& discard_padding() const {
     DCHECK(!end_of_stream());
     return discard_padding_;
   }
 
   void set_discard_padding(const DiscardPadding& discard_padding) {
     DCHECK(!end_of_stream());
     discard_padding_ = discard_padding;
   }
@@ skipping 54 matching lines @@
 
   // Constructor helper method for memory allocations.
   void Initialize();
 
   DISALLOW_COPY_AND_ASSIGN(DecoderBuffer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECODER_BUFFER_H_