- Expose CanvasPixelArray functionality directly in JavaScript

- Expose CanvasPixelArray functionality directly in JavaScript
  indexed property accesses.
- The IC stubs have not been updated to handle these directly, but
  at least we do not have to leave the VM to access bytes.

Review URL: http://codereview.chromium.org/159263

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2549 ce2b1a6d-e550-0410-aec6-3dcde31c8c00