Tests overriding user agent via WebInspector extension API

Started extension.
Running tests...
RUNNING TEST: extension_testUserAgent
navigator.userAgent: Mozilla/4.0 (compatible; WebInspector Extension User-Agent override; RSX-11M)
user-agent header for extensions-useragent.html: Mozilla/4.0 (compatible; WebInspector Extension User-Agent override; RSX-11M)
user-agent header for xhr-exists.html: Mozilla/4.0 (compatible; WebInspector Extension User-Agent override; RSX-11M)
All tests done.