Revert 236651 "Linux: initialize RenderSandboxHostLinux before t..."

This change seems to break some browser_tests on linux debug.
Some examples are in the trybot results at the original CL, including some
PnaclHeaderTests, locally I saw it break DeclarativeApiTest.DeclarativeApi.
Look for "FATAL:render_sandbox_host_linux.cc(712)] Check failed: 1 == base::GetNumberOfThreads(base::GetCurrentProcessHandle()) (1 vs. 2)"
in the output.

> Linux: initialize RenderSandboxHostLinux before threads are started.
> 
> RenderSandboxHostLinux::Init() uses fork(). Therefore the process needs
> to only have one thread when this is called.
> 
> Move RenderSandboxHostLinux early enough that on one thread exists.
> 
> BUG=321388
> R=creis@chromium.org, kbr@chromium.org, oshima@chromium.org
> 
> Review URL: https://codereview.chromium.org/77123002

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/82743002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236693 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236693