[perf-test] Add a binding benchmark for div.getAttribute()

[perf-test] Add a binding benchmark for div.getAttribute()
https://bugs.webkit.org/show_bug.cgi?id=86814

Reviewed by Ryosuke Niwa.

We should remove Bindings/dom-attributes.html and instead add more
reasonable micro benchmarks by classifying DOM binding call paths.

This patch adds a benchmark for div.getAttribute(). This benchmark
covers 'getAttribute' in Dromaeo/dom-attr.html, and other DOM methods
that return a String.

Test results in my Linux desktop:

RESULT Bindings: get-attribute= 250.088158538 runs/s
median= 250.469728765 runs/s, stdev= 4.66551901315 runs/s, min= 240.673886883 runs/s, max= 256.739409499 runs/s

RESULT Bindings: get-attribute= 250.209764698 runs/s
median= 250.626959986 runs/s, stdev= 4.12030002477 runs/s, min= 241.254523522 runs/s, max= 255.102040816 runs/s

RESULT Bindings: get-attribute= 248.907532887 runs/s
median= 250.312891114 runs/s, stdev= 3.23173125874 runs/s, min= 240.673886883 runs/s, max= 251.572327044 runs/s

RESULT Bindings: get-attribute= 250.243680844 runs/s
median= 250.783797637 runs/s, stdev= 4.19327170024 runs/s, min= 240.963855422 runs/s, max= 255.102040816 runs/s

RESULT Bindings: get-attribute= 245.329046608 runs/s
median= 244.948040416 runs/s, stdev= 2.24314248534 runs/s, min= 240.384615385 runs/s, max= 248.756218905 runs/s

* Bindings/get-attribute.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117550 268f45cc-cd09-0410-ab3c-d52691b4dbfc