GitLab

This CL (hopefully) removes all calls to these methods in content:
- MessageLoop::PostTask
- MessageLoop::PostDelayedTask
- MessageLoop::DeleteSoon
- MessageLoop::ReleaseSoon
- MessageLoop::Run
- MessageLoop::RunUntilIdle

BUG=616447
R=avi@chromium.org

Review-Url: https://codereview.chromium.org/2312803003
Cr-Commit-Position: refs/heads/master@{#416734}