HAR content size is not compliant to the spec

[Lesterpig]

Hello, I believe there is a difference between the HAR specification and selenium-wire's implementation.

Spec: http://www.softwareishard.com/blog/har-12-spec/#content

size [number] - Length of the returned content in bytes. Should be equal to response.bodySize if there is no compression and bigger when the content has been compressed.
compression [number, optional] - Number of bytes saved. Leave out this field if the information is not available.

Implementation: https://github.com/wkeeling/selenium-wire/blob/master/seleniumwire/har.py#L87

            "content": {
                "size": response_body_size, # Compressed size
                "compression": response_body_compression, # Difference between decoded and compressed size
                "mimeType": flow.response.headers.get('Content-Type', ''),
            },
            "redirectURL": flow.response.headers.get('Location', ''),
            "headersSize": len(str(flow.response.headers)),
            "bodySize": response_body_size, # Compressed size

My understanding is that size should actually be equal to response_body_decoded_size, and be different from bodySize. Am I right? If yes, let me know and I will propose a short pull request.