Fix code generated matchers to handle recursive objects.

Fix code generated matchers to handle recursive objects.

This requires using a wrapper that creating the matchers lazily (when
they're first used), so that a matcher can refer to itself without
causing a circularity during initialization.

R=jwren@google.com

Committed: https://code.google.com/p/dart/source/detail?r=39274

[jwren, 2014-08-14 22:37:56]

LGTM

[Paul Berry, 2014-08-14 22:45:06]

Committed patchset #1 manually as r39274 (presubmit successful).