IDL compiler: [Conditional] for methods

Some Perl whitespace changes, to match consistent Python.

BUG=239771

Review URL: https://codereview.chromium.org/60013006

git-svn-id: svn://svn.chromium.org/blink/trunk@161432 bbb929c8-8fbe-4397-9dbb-9b2b20218538