Pass "-std" flag to YCM config.

"-std" has value which is not equal to default value "c++11" for some variants
of Chrome build. At least for "chromeos=1 clang=1" build "-std=gnu++11" is set.
So not passing "-std" to YCM caused compilation error inside YCM, hence there
were some problems with completion.

BUG=none
NOTRY=true

Review URL: https://codereview.chromium.org/104503016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243862 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243862