GitLab

Actually test that the sessionStorage behaved correctly. Also, add a test for a
conflict case. Ensure the page still loads.

BUG=none
TEST=PrerenderBrowserTest.PrerenderPageNewTab,
     PrerenderBrowserTest.PrerenderSessionStorageConflict

Review URL: https://codereview.chromium.org/129383002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244066 0039d316-1c4b-4281-b951-d872f2087c98