Add mojo_idl_generator.gypi
NOT FOR REVIEW
BUG=
R=darin@chromium.org

Review URL: https://codereview.chromium.org/53173008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234233 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234233