use the stream instead of the cursor data to return its size

Most content providers set up the data size in the cursor that
provides the file name, but sound recorder does not. Use the
stream size instead, which will work with all sources and
probably is no slower.

fixes http://b/2529352 http://b/2524574

Change-Id: I32d101d07ca1d0fa2ff17c3c68393356902096d3