Initialize the response filter. Will only be called a single time. The filter will not be installed if this function returns false (0).

Called to filter a chunk of data. Expected usage is as follows:

1. Read input data from |data_in| and set |data_in_read| to the number of bytes that were read up to a maximum of |data_in_size|. |data_in| will be NULL if |data_in_size| is zero. 2. Write filtered output data to |data_out| and set |data_out_written| to the number of bytes that were written up to a maximum of