[Performance Tests] [Chromium] Bindings/dom-attributes.html is timing out

[Performance Tests] [Chromium] Bindings/dom-attributes.html is timing out
https://bugs.webkit.org/show_bug.cgi?id=79593

Reviewed by Adam Barth.

This patch halves the execution time of Bindings/dom-attributes.html
in order to avoid timeout in Chromium. The reason for the timeout is that
V8 DOM bindings are too much slower than JSC bindings.
I am a bit afraid that this patch will reduce the accuracy of the
perf test results, but it would make sense to reduce the execution time
until we fix the performance issue in V8 DOM bindings.

* Bindings/dom-attributes.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108942 268f45cc-cd09-0410-ab3c-d52691b4dbfc