media: Support transporting 0-byte DecoderBuffer over mojo

media/mojo/common/mojo_decoder_buffer_converter.cc

 // 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.
 
 #include "media/mojo/common/mojo_decoder_buffer_converter.h"
 
 #include <memory>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 85 matching lines @@
   }
 
   DCHECK(!read_cb_);
   DCHECK(!media_buffer_);
   DCHECK_EQ(bytes_read_, 0u);
 
   scoped_refptr<DecoderBuffer> media_buffer(
       mojo_buffer.To<scoped_refptr<DecoderBuffer>>());
   DCHECK(media_buffer);
 
-  if (media_buffer->end_of_stream()) {
+  // A non-EOS buffer can have zero size. See http://crbug.com/663438
+  if (media_buffer->end_of_stream() || media_buffer->data_size() == 0) {

[chcunningham, 2016/11/08 22:00:38]

Could these be simplified to simply if (!media_buffer->data_size())?

[xhwang, 2016/11/08 22:13:51]

We can't call anything (including data_size()) if the buffer is EOS:

https://cs.chromium.org/chromium/src/media/base/decoder_buffer.h?rcl=0&l=106

     std::move(read_cb).Run(media_buffer);
     return;
   }
 
   // Read the data section of |media_buffer| from the pipe.
   read_cb_ = std::move(read_cb);
   media_buffer_ = std::move(media_buffer);
   ReadDecoderBufferData();
 }
 
@@ skipping 95 matching lines @@
         << ": Failed to write DecoderBuffer becuase the pipe is already closed";
     return nullptr;
   }
 
   DCHECK(!media_buffer_);
   DCHECK_EQ(bytes_written_, 0u);
 
   mojom::DecoderBufferPtr mojo_buffer =
       mojom::DecoderBuffer::From(media_buffer);
 
-  if (media_buffer->end_of_stream())
+  // A non-EOS buffer can have zero size. See http://crbug.com/663438
+  if (media_buffer->end_of_stream() || media_buffer->data_size() == 0)
     return mojo_buffer;
 
   // Serialize the data section of the DecoderBuffer into our pipe.
   media_buffer_ = media_buffer;
   MojoResult result = WriteDecoderBufferData();
   return IsPipeReadWriteError(result) ? nullptr : std::move(mojo_buffer);
 }
 
 void MojoDecoderBufferWriter::OnPipeError(MojoResult result) {
   DVLOG(1) << __FUNCTION__ << "(" << result << ")";
@@ skipping 42 matching lines @@
     if (bytes_written_ == buffer_size) {
       media_buffer_ = nullptr;
       bytes_written_ = 0;
     }
   }
 
   return result;
 }
 
 }  // namespace media