- move textZoom storage to the prescontext from the documentviewer
- copy the textZoom between document viewers for fastback
r=bryner sr=dbaron a=cbeard
git-svn-id: svn://10.0.0.236/branches/MOZILLA_1_8_BRANCH@177691 18797224-902f-48f8-a5cc-f745e15eee43