[perf-test] Add a binding benchmark for getElementById()

[perf-test] Add a binding benchmark for getElementById()
https://bugs.webkit.org/show_bug.cgi?id=86808

Reviewed by Ryosuke Niwa.

Currently Bindings/dom-attributes.html is just a collection
of random DOM attributes and methods. We should remove it and
instead add more reasonable micro benchmarks by classifying
DOM binding call paths.

This patch adds a benchmark for document.getElementById(),
which covers other DOM methods that return a Node Object.

The reason why we want to add a benchmark for document.getElementById()
in spite of the fact that Dromaeo/dom-query.html is already testing
document.getElementById(), is that Dromaeo/dom-query.html outputs one
result for several benchmarks (i.e. getElementById().nodeType,
getElementsByTagName()[0].nodeType etc), and thus we cannot observe
regression of getElementById() itself. (Catching regression of
getElementById() would be critical.)

Test results in my Linux desktop:

RESULT Bindings: get-element-by-id= 300.933707795 runs/s
median= 302.267002519 runs/s, stdev= 3.04954648504 runs/s, min= 295.930949445 runs/s, max= 305.34351145 runs/s

RESULT Bindings: get-element-by-id= 302.030324483 runs/s
median= 302.267481977 runs/s, stdev= 1.78518068367 runs/s, min= 298.507462687 runs/s, max= 304.568527919 runs/s

RESULT Bindings: get-element-by-id= 301.993483538 runs/s
median= 302.648171501 runs/s, stdev= 1.87604126626 runs/s, min= 296.662546354 runs/s, max= 304.568527919 runs/s

RESULT Bindings: get-element-by-id= 301.936607982 runs/s
median= 302.45758701 runs/s, stdev= 1.88991087072 runs/s, min= 298.879202989 runs/s, max= 304.955527319 runs/s

RESULT Bindings: get-element-by-id= 301.952234563 runs/s
median= 302.648171501 runs/s, stdev= 1.59929752614 runs/s, min= 299.625468165 runs/s, max= 304.568527919 runs/s

* Bindings/get-element-by-id.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117548 268f45cc-cd09-0410-ab3c-d52691b4dbfc