Try time (decode) and size for null glyf/loca xform vs regular vs woff1

As requested in https://www.w3.org/Fonts/WG/track/actions/186 I ran a
variety of compress/decompress scenarios over the Google Fonts collection.

Main findings are:

 * WOFF2 decompression uses less memory than woff, more than brotli
standalone.

 * WOFF2 decompression was faster than WOFF at min, median, and average but
has a higher standard deviation and max.

 * Applying brotli (using the "bro" utility; https://github.com/go
ogle/brotli/blob/master/tools/bro.cc) directly to a font (to simulate use
via Accept-Encoding: br) resulted in a file that was larger than a
transformed woff2 but fastest to decompress.

 * WOFF2 decompression is slightly faster when there are no transforms. The
most significant improvement is lower standard deviation and worst-case
time.

The brotli codebase is probably the most carefully optimized of the
implementations I compared. WOFF2 without transform could likely be sped
up, though some work is hard to dodge without violating the spec. For
example, "the decoder MUST recalculate the checkSum value for each decoded
table."

Summary and raw results can be seen in https://docs.google.com/
spreadsheets/d/1_ZYTFaG6_NJy7n_t-RpPDXCAZIKDP_1SXiJQz0o8QMg/edit#gid=
367643030.

Cheers, Rod S.