Add DCHECKs to the states that should be entered only when the previous state succeeded.
Add DCHECKs to the states that should be entered only when the
previous state succeeded.

R=ibrar,phajdan.jr
BUG=http://crbug.com/4965
TEST=none
Review URL: http://codereview.chromium.org/149013

git-svn-id: http://src.chromium.org/svn/trunk/src@19394 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 62a344754532a025f14920774d80eeba15d9cfb9
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser