End the SafeBrowsing update cycle when the update response contains no chunk URLs (i.e. the client is up to date).
End the SafeBrowsing update cycle when the update response
contains no chunk URLs (i.e. the client is up to date).

We currently don't handle this case properly, which results
in a DCHECK being hit.

BUG=6049 (http://crbug.com/6049)

Review URL: http://codereview.chromium.org/18181

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@8244 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