Remove call to set task priority of WebKit2 processes on Mac
https://bugs.webkit.org/show_bug.cgi?id=111239

Patch by Kiran Muppala <cmuppala@apple.com> on 2013-03-01
Reviewed by Darin Adler.

Remove call to set task prioirty of WebKit2 processes on Mac as it
is no longer necessary.

* Shared/mac/ChildProcessMac.mm:
(WebKit::ChildProcess::platformInitialize): Remove call to setpriority().

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144528 268f45cc-cd09-0410-ab3c-d52691b4dbfc