Adding `content_security_policy` to 10 sample extensions.

Touched:
* contentSettings
* contextMenus/basic
* browserAction/set_icon_path
* app_launcher
* devtools/network/chrome-firephp
* extension/isAllowedAccess
* news_a11y
* notifications
* omnibox/extension-docs
* pageAction/pageaction_by_url

As a drive-by, fixed the broken `contentscript_xhr` by changing to Twitter's
new API endpoint

BUG=92644
TEST=

Review URL: http://codereview.chromium.org/8309001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107084 0039d316-1c4b-4281-b951-d872f2087c98
52 files changed