REGRESSION(r219640): Speedometer no longer runs on Safari 7

REGRESSION(r219640): Speedometer no longer runs on Safari 7
https://bugs.webkit.org/show_bug.cgi?id=175749

Reviewed by Joseph Pecoraro.

PerformanceTests:

Use regular string instead of template literal to make the script compatible with older versions of Safari.

* Speedometer/resources/benchmark-runner.js:
(BenchmarkRunner.prototype._runTest):

Websites/browserbench.org:

Fix the bug on browserbench.org.

* Speedometer/resources/benchmark-runner.js:
(BenchmarkRunner.prototype._runTest):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220950 268f45cc-cd09-0410-ab3c-d52691b4dbfc