gypd: update with required default variables.

Update the list of identity variables in gypd so that the generator will
run successfully on Chromium, which uses these variables predefined by
other generators.

BUG=
R=bradnelson@google.com

Review URL: https://codereview.chromium.org/642933007

git-svn-id: http://gyp.googlecode.com/svn/trunk@1989 78cadc50-ecff-11dd-a971-7dbc132099af