Generate callback IDLs with code generator in python

With this patch, all 32 callback IDLs are generated with
code generator in python.

R=haraken@chromium.org
BUG=262365
TEST=no tests. refactoring.

Review URL: https://chromiumcodereview.appspot.com/21224002

git-svn-id: svn://svn.chromium.org/blink/trunk@155247 bbb929c8-8fbe-4397-9dbb-9b2b20218538