GitLab

TEST=Open about:system. Table containing available system information is shown.
Clicking on button Expand shows associated entry, and clicking on Collapse hides it. Initialy all entries are hidden. 
Clicking on Expand all / Collapse all shows / hides all entries.
about:system/foo hides all entries but foo, and scrolls to it  

BUG=4973

Review URL: http://codereview.chromium.org/3173038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@57288 0039d316-1c4b-4281-b951-d872f2087c98