Update te way test shell cleans up on exit.
Update te way test shell cleans up on exit.

It turns out that the LayoutTestControllers are only reset
when a test is started.  Some tests leave sub-windows open
(e.g. http/tests/security/aboutBlank/security-context-window-open.html)
When these tests are run through the purify runner - which
only runs one test per test shell - the effect is that the 
LayoutTestController does not get cleaned up.

BUG=5329

Review URL: http://codereview.chromium.org/18300

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@8231 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,adobe/chromium