Cherry-pick: Set thread names to be visible in debuggers

Cherrypick of upstream trunk r250981

> Like linux, on android we can get the thread names to show up in the
> debugger by setting the process name for the LWP.
>
> This change sets the name of the calling thread using prctl.
>
> BUG=332881
>
> R=jam@chromium.org
> R=torne@chromium.org
>
> Review URL: https://codereview.chromium.org/144943004

Bug: 13577599
Change-Id: I5f350bcb078f27ace005168d414bfc84d26b012b
1 file changed