Revert 160985 "Enable -Wall on Linux as well."

Breaks Linux Clang compile badly.

> Enable -Wall on Linux as well.
> 
> BUG=312287
> TBR=dglazkov
> 
> Review URL: https://codereview.chromium.org/53223002

TBR=l.gombos@samsung.com

Review URL: https://codereview.chromium.org/54003002

git-svn-id: svn://svn.chromium.org/blink/trunk@161012 bbb929c8-8fbe-4397-9dbb-9b2b20218538