Adds chunk_size to CompressingFileReader.

Before when iterating using this object, the call to the underlying file object
was made without a chunk_size.  This is bad because this would cause the entire
contents of the file to be read.

Change-Id: I9956e5d2d693a6260252fff331d4f78f70179a6c
Merge "Adds chunk_size to CompressingFileReader."