Use max_enforcement_level rather than true/false in TrackedPreferenceMetadata.

Review URL: https://codereview.chromium.org/138093004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249742 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249742
Tooltip controller: set tooltip_window_ to NULL in OnCancelMode.

BUG=341355
TEST=view_unittests, manually verify bug does not repro.
R=sky@chromium.org, xiyuan@chromium.org

Review URL: https://codereview.chromium.org/146033004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249743 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249743