[Performance test] In perftest.py, do not include 'description' in 'results'

[Performance test] In perftest.py, do not include 'description' in 'results'
https://bugs.webkit.org/show_bug.cgi?id=86696

Reviewed by Csaba Osztrogoná.

'results' in perftest.py should not include any data that is not expected
by the perf bot server. We do not need to send 'description' to the perf bot
server since 'description' is always the same.

Thus this patch just removes 'description' from 'results'.

* Scripts/webkitpy/performance_tests/perftest.py:
(PerfTest.parse_output):
(PerfTest.output_statistics):
(ChromiumStylePerfTest.parse_output):
(PageLoadingPerfTest.run):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117422 268f45cc-cd09-0410-ab3c-d52691b4dbfc