Only commit cookie changes in prerenders after a prerender is shown
Will create a PrerenderCookieStore for each prerender, retaining all cookie
operations of a prerender until the prerender is shown to the user.
Forces prerenders to be in a new render process by themselves for this to work.
This is a resubmission of https://codereview.chromium.org/
233353003, which had
to be reverted due to build breaks. See LGTM's there.
BUG=371003
TBR=jam@chromium.org
Review URL: https://codereview.chromium.org/
280403002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270049 0039d316-1c4b-4281-b951-d872f2087c98