8a021512a2
This also removed the code from content, which doesn't belong there because it's for a feature in Chrome. In order to implement this in a unified way, I needed to create a public interface around ChildThread. A lot of the change is updating callers of ChildThread to use ChildThreadImpl instead. BUG=448473 Review URL: https://codereview.chromium.org/897563002 Cr-Commit-Position: refs/heads/master@{#314367}