Revert 227685 "Added the Prerender.ModPagespeedHeader.* histogra..."

> Added the Prerender.ModPagespeedHeader.* histograms to histograms.xml. 
> Extended the data extraction to also handle X-Page-Speed headers.
> 
> (dup of 20832003 which I can't commit with my personal email account)
> 
> BUG=267695
> 
> Review URL: https://codereview.chromium.org/26279004

This test caused a leak on the memory bots. Details can be found here:
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%283%29/builds/30782/

TBR=matterbury@google.com

Review URL: https://codereview.chromium.org/26670002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227696 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227696