ability to filter or manipulate content as it's passed through.
Create two example tests using this utility that cause
updates to close early to test resumes, and to add delays
to make sure the update still completes correctly.
What other tests should be created for this?
BUG=chromium-os:8207
TEST=Run by hand
Review URL: http://codereview.chromium.org/5632002
Change-Id: Iefb8c8e223fb2ba6bad2c551f7c4403a0bec6ecf
