Fix multi-column test flake

Both tests just needed to force a layout before running the
real part of the test to avoid flake.

Review URL: https://codereview.chromium.org/26386003

git-svn-id: svn://svn.chromium.org/blink/trunk@159091 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: [Conditional]

Conditional is deprecated, but still used *many* places.
The main 'generate_conditional_string' function and template value ('contents')
are already there; this is just using it in the template.

I've implemented this via a Jinja custom filter:
http://jinja.pocoo.org/docs/api/#custom-filters
...and a {% filter %} block:
http://jinja.pocoo.org/docs/templates/#id7
...which means this adds only 2 lines to each use in the template,
rather than the 6-8 lines of having 2 {% if %} blocks.
(Need to change Perl to regularize inconsistent spacing.)

Docs:
https://sites.google.com/a/chromium.org/dev/blink/webidl/blink-idl-extended-attributes#TOC-Conditional-i-m-a-deprecated

BUG=239771

Review URL: https://codereview.chromium.org/26233002

git-svn-id: svn://svn.chromium.org/blink/trunk@159092 bbb929c8-8fbe-4397-9dbb-9b2b20218538