GitLab

In this CL, we split the creation of the BrowserThread::IO thread and
initialization of its delegate:

1. The BrowserThread::IO is created in the
   BrowserMainLoop::PostMainMessageLoopStart() after the UI thread
   is created. Adjust the tracing events in the BrowserMainLoop.
2. Simplify the logic in BrowserMainLoop::CreateThreads() since only
   the launcher thread is created there. Initializes the
   delegate of the BrowserThread::IO there.
3. Update the logic in the BrowserThreadImpl when checking whether
   the BrowserThread::IO has initialized.
4. Update BrowserMainLoopTest and BrowserProcessImplTest.

 This is the first step of starting ServiceManager earlier.

Bug: 729596
Change-Id: I7a08fd7c7bf5548f8039c8c38152ecfde3bd20c4
Reviewed-on: https://chromium-review.googlesource.com/905424
Commit-Queue: Xi Han <hanxi@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537318}