Test CSS.getAllStyleSheets returns expected information for different style sheet sources.

PASS: There should be four stylesheets.

URL: inspector/css/resources/external.css
OFFSET: (0, 0)
PASS: Stylesheet should have a frame.

URL: <style> on inspector/css/getAllStyleSheets.html
OFFSET: (5, 7)
PASS: Stylesheet should have a frame.

URL: <style> on inspector/css/getAllStyleSheets.html
OFFSET: (6, 7)
PASS: Stylesheet should have a frame.

URL: inspector/css/getAllStyleSheets.html
OFFSET: (0, 0)
PASS: Stylesheet should have a frame.