CanvasPathMethods should be shared with CRC2D and Path2D

All methods in CanvasPathMethods should be shared with CanvasRenderingContext2D and Path2D.
CanvasPathMethods has been differently defined in CRC2D and Path2D until now.
It is against the spec and it makes it more difficult to maintain.
Actually, CRC2D.idl has defined ellipse function but Path2D.idl has omitted the function.
Following codes will make trouble.

  var path = new Path();
  path.ellipse(100, 100, 50, 50, 0, 0, 6.28, false); // undefined error

To solve this problem, it should be changed to share CanvasPathMethods with CRC2D and Path2D.
And to prevent happening same problem, we should add layout test with respect to all Path2D methods.

Spec:
  http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas/#canvaspathmethods

Review URL: https://codereview.chromium.org/191923002

git-svn-id: svn://svn.chromium.org/blink/trunk@169316 bbb929c8-8fbe-4397-9dbb-9b2b20218538