Assigning to __proto__ is a fast way to stitch together a number of
object literals into a prototype chain without copying all the
properties.
Unfortunately this leads to very slow execution on Firefox (and
jsshell). So now we feature-detect Chrome (and d8) since that is the
only browser we know currently can use the 'fast' startup path without
penalizing subsequent performance.
This speeds up some jsshell benchmarks by 30%.
R=het@google.com
Review URL: https://codereview.chromium.org/2180533002 .
Stephen Adams
5923966da3