Remove --ppapi-flash-in-process flag.

a) I'm pretty sure it mostly doesn't work anymore (it's been at least
sort of broken for a long time). b) I'm pretty sure no one uses it.

BUG=344054
R=yzshen@chromium.org
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/168603002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251635 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251635