Unify desktop and Android tab helper instantiation.

BUG=337600
TEST=zero visible change

Review URL: https://codereview.chromium.org/144443003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247676 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247676