- Add copy constructors.
- Add subarray methods.
- Make instanceof and constructor property work.
- Rename PixelArray to Uint8ClampedArray.

Also fix broken definition of assertInstanceof in MJSUnit test harness.

R=mstarzinger@chromium.org
BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10558005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11949 ce2b1a6d-e550-0410-aec6-3dcde31c8c00