xhr.use() returns this, making xhr.submit() chainable

Change-Id: I309389f0c9eb0777c553d79fd2c2ac66fbff30f5
Widgets now use reference chain when submitting their xhr objects

Change-Id: Idafc2b1bf18bdbfcb01d376534924ddb25ac7163
Removed arguments.callee for strict mode compliance

Change-Id: I3d35d00e8a03cdd30a4573a0b8ba8c68af739cba