Refactor WritableBuffer interface for more useful ptr management.

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
===================================================================
--- media/filters/ffmpeg_audio_decoder.cc	(revision 20532)
+++ media/filters/ffmpeg_audio_decoder.cc	(working copy)
@@ -107,9 +107,9 @@
 
   // If we have decoded something, enqueue the result.
   if (output_buffer_size) {
-    DataBuffer* result_buffer = new DataBuffer();
-    memcpy(result_buffer->GetWritableData(output_buffer_size),
-           output_buffer, output_buffer_size);
+    DataBuffer* result_buffer = new DataBuffer(output_buffer_size);
+    uint8* data = result_buffer->GetWritableData();
+    memcpy(data, output_buffer, output_buffer_size);
 
     // Determine the duration if the demuxer couldn't figure it out, otherwise
     // copy it over.
@@ -131,7 +131,7 @@
   // 2. FFmpeg didn't output anything.
   // 3. An end of stream buffer is received.
   if (result == 0 && output_buffer_size == 0 && input->IsEndOfStream()) {
-    DataBuffer* result_buffer = new DataBuffer();
+    DataBuffer* result_buffer = new DataBuffer(0);
     result_buffer->SetTimestamp(input->GetTimestamp());
     result_buffer->SetDuration(input->GetDuration());
     EnqueueResult(result_buffer);