Revert "Reland "Start ServiceManger before creating BrowserMainLoop.""

This reverts commit f481306ad989755ebe61cfed4ab2a4fa53044b29 and
disables following tests on Windows:
 * RenderThreadImplBrowserTest.NonResourceDispatchIPCTasksDontGoThroughScheduler
 * UserScriptListenerTest.NavigationWaitsForContentScriptsToLoad

Reason for revert: Causes BrowserMainLoopTest, CreateThreadsInSingleProcess to fail every time content_unittests is run, if DCHECKs are enabled.

Original change's description:
> Reland "Start ServiceManger before creating BrowserMainLoop."
>
> This relands commit aa60c219407f1158214858e83e5456e42dcfe891. The original CL
> (https://crrev.com/c/1113802) got reverted becuase FeatureList and field
> trials are not setup properly in early startup in Android WebView, but
> ServiceMangerContext has checked features. See crbug.com/899376. The fix is
> in a separate CL: https://crrev.com/c/1305876. Another related precursor CL
> is: https://crrev.com/c/1308096.
>
> This CL is an exact copy of the original CL.
>
> The original cl description is:
> This CL instantiates the ServiceManagerContext before creating
> the BrowserMainRunner. It splits the startup path into two,
> with/without starting the full browser. The changes are implemented
> behind a flag "allow-start-service-manager-only".
>
> Bug: 846846,729596
> TBR: jam@chromium.org
> Change-Id: I5214af850d4ef256c9d223db059ed009a42de714
> Reviewed-on: https://chromium-review.googlesource.com/c/1305822
> Commit-Queue: Xi Han <hanxi@chromium.org>
> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#604969}

TBR=gab@chromium.org,jam@chromium.org,hanxi@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 846846, 729596, 902311
Change-Id: I8b46711602a240023f4a03a69aa70f66d4eee726
Reviewed-on: https://chromium-review.googlesource.com/c/1322343
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606004}
11 files changed