Fix deadlock in ChildProcessService.onDestroy()

Fix deadlock in ChildProcessService.onDestroy()

onCreate() spawns the CrMain thread. onDestroy() can happen quickly
after onCreate() (for example if the browser crashes),
so we have to be careful about blocking on any semaphores
wrt the CrMain thread.

The existing cmdline check did not cover all of that.

In addition we have to avoid deadlocks between
nativeShutdownMainThread()and us actually not having ever
entered native main().
(ChildThreadImpl::Shutdown() on Android waits on a
condition variable.)

BUG=448549, 457406, 457914
NOTRY=True

Review URL: https://codereview.chromium.org/1052133002

Cr-Commit-Position: refs/heads/master@{#323567}

Committed: https://chromium.googlesource.com/chromium/src/+/4d95abadb6d081349c9d4e3ffb0036c575e92567

[no sievers, 2015-04-07 02:07:34]

Committed patchset #1 (id:1) manually as
4d95abadb6d081349c9d4e3ffb0036c575e92567 (tree was closed).