Upgrade es5-shim package.

Change-Id: I3b00ebbbe2100306ca72e53dd822af047cdd9a31
Make scroll-to-bottom work reliably after images are loaded.

We can't use a event listener on the top-level document, because the
load events don't bubble.  So create onload (and onloadstart and onloadend)
event handlers on the image tag itself, to ensure that we scroll after the
image has finished loading.

Change-Id: I9f1d8e9a40016075b8ee5e61aa62f6af02a4ff3c