Copy properties by descriptor.
Symptom: target is null, causing target.children to fail.
Analysis: The failure is in items() called from registerElement(),
that's impossible. Actually it's 'get items()' and the call is triggered
inside the proxy by a [[Get]] on the proxy object.
Fix: Copy by getOwnPropertyDescriptor -> defineProperty.
Sync to traceur-compiler master
Test case for InvalidStateError: Failed to execute 'dispatchEvent'
   on 'EventTarget': The event provided is null.
Analysis: The dispatchEvent() is called from a function higher
on the proto chain than createdCallback() and these functions
are not being marked as expandos.
Remove the 'override' function.
Implement all of the proxy handlers, including has()
Correct the FakePlayer proto chain.
Now that the recorder is correctly building
JSON _fake_proto values, the FakePlayer needed to
also build the proto chain correctly.
Guard more logging. Pica loads
Add test for an undefined proto during playback.
_fake_proto can be undefined
Now we depend upon the master branch for
https://github.com/johnjbarton/harmony-reflect
until the root harmony-reflect is fixed up.
Don't exclude window.location