Add tests for clipping ASSERT

We disabled clip caching due to bugs, which fixed the asserts in the associated
bug. This CL captures those test cases as LayoutTests so we don't re-introduce
the issue when we enable the clip cache again.

BUG=365474

Review URL: https://codereview.chromium.org/259083004

git-svn-id: svn://svn.chromium.org/blink/trunk@172832 bbb929c8-8fbe-4397-9dbb-9b2b20218538