gypd: update with required default variables.

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

Committed: https://code.google.com/p/gyp/source/detail?r=1989

[Torne, 2014-10-10 12:57:47]

torne@chromium.org changed reviewers:
+ bradnelson@chromium.org

[bradn, 2014-10-12 20:21:44]

bradnelson@google.com changed reviewers:
+ bradnelson@google.com

[bradn, 2014-10-12 20:21:44]

lgtm

[Torne, 2014-10-13 08:43:39]

Committed patchset #1 (id:1) manually as 1989 (presubmit successful).