REGRESSION(r164764): 2% regressions on DYEBench and 5% regressions on cssquery-dojo and dom-traverse

[Ryosuke Niwa]

According to perf.webkit.org, http://trac.webkit.org/changeset/164764 caused 5-10% regressions on various DOM benchmarks:

https://perf.webkit.org/#mode=charts&chartList=%5B%5B%22mac-mavericks%22%2C%22Dromaeo%2Fcssquery-dojo%3ARuns%22%5D%2C%5B%22mac-mountainlion%22%2C%22Dromaeo%2Fcssquery-dojo%3ARuns%22%5D%2C%5B%22mac-mountainlion%22%2C%22Dromaeo%2Fcssquery-dojo%3ARuns%22%5D%2C%5B%22mac-mavericks%22%2C%22Dromaeo%2Fcssquery-dojo%3ARuns%22%5D%2C%5B%22mac-mavericks%22%2C%22DoYouEvenBench%2FFull%3ATime%3ATotal%22%5D%2C%5B%22mac-mountainlion%22%2C%22DoYouEvenBench%2FFull%3ATime%3ATotal%22%5D%5D

Most notably, there is 2% regression on DYEBench.

[Radar WebKit Bug Importer]

<rdar://problem/16203575>

[Ryosuke Niwa]

Also regressed Dromaeo/dom-traverse by 5%:

https://perf.webkit.org/#mode=charts&chartList=%5B%5B%22mac-mountainlion%22%2C%22Dromaeo%2Fdom-traverse%3ARuns%22%5D%5D&days=39