Fixed CSP warnings in the sample extension for device info API.

BUG=170375
NOTRY=true

Review URL: https://codereview.chromium.org/24417003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225676 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225676