Fixing reopening of tabs after relaunch by preventing reentry into AttemptExit process.

TESTS=Please follow steps as outlined in the bug report.
R=cpu@chromium.org, ananta@chromium.org
BUG=318503

Review URL: https://codereview.chromium.org/102403004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238467 0039d316-1c4b-4281-b951-d872f2087c98
Fix mention of RVHM in comments.

BUG=314791
TEST=No behavior change.
R=nasko@chromium.org

Review URL: https://codereview.chromium.org/101863005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238468 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238468