Test that CanvasAgent tracks changes in the client nodes of a CSS canvas.


== Running test suite: Canvas.requestClientNodes.CSS
-- Running test case: Canvas.requestClientNodes.CSS.Create
PASS: Canvas with created client should have CSS name "css-canvas".
PASS: There should be one client node.
PASS: Client node "div" is valid.

-- Running test case: Canvas.requestClientNodes.CSS.Destroy
PASS: Canvas with destroyed client should have CSS name "css-canvas".
PASS: There should be no client nodes.