Fix crash when reusing possibly stale NavigationState in user script code.
Fix crash when reusing possibly stale NavigationState in
user script code.

BUG=56323
TEST=Install autopagerize extension. Go to google.com, search 'monkey', press enter, refresh. Should not
crash.

Review URL: http://codereview.chromium.org/3916001

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@63161 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser