Fix crash reporting of child process command line switches.

It's not immediatley clear to me how this broke, since I converted all the
callsites of the old method. However I've verified on each platform that this
now reports command line switches properly.

BUG=77656,298225

Review URL: https://codereview.chromium.org/25733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226519 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226519