Change DemuxerStream::ReadCallback to use ref-counted buffers.

media/base/mock_reader.h

Index: media/base/mock_reader.h
diff --git a/media/base/mock_reader.h b/media/base/mock_reader.h
index c8a5e8cfb8a77f06204a8a53606825fde2d11546..a6122a9ce826f41ac05048aa00933a6eafac43af 100644
--- a/media/base/mock_reader.h
+++ b/media/base/mock_reader.h
@@ -50,7 +50,7 @@ class MockReader
   bool expecting_call() { return expecting_call_; }
 
  private:
-  void OnReadComplete(BufferType* buffer) {
+  void OnReadComplete(const scoped_refptr<BufferType>& buffer) {
     DCHECK(!called_);
     DCHECK(expecting_call_);
     expecting_call_ = false;